(CNN) Congress is expected to vote on a massive $1.3 trillion spending package this week that keeps all of the government funded, but what controversial policy riders tucked inside are the thing to watch?

Lawmakers could settle months-long disagreements over Obamacare stabilization money, school safety funding, a contentious rail program and immigration.

Or, they may leave them all unresolved.

The colossal package would keep the government funded through the end of September and could include money to help lower premiums in the Affordable Care Act marketplace as well as money for the Gateway project, a rail program that involves constructing a tunnel for New York and New Jersey commuters beneath the Hudson River ( that is, if President Donald Trump doesn't block it ).

Lawmakers say that they expect the details of what is in the bill to be revealed as soon as Monday, when members return from the weekend. Then lawmakers will have just a matter of days to pass it before the March 23 deadline. If they can't find consensus on a handful of outstanding issues, Congress would be forced to pass yet another short-term spending bill or face a shutdown.

That and many other tasks already awaited Congress before Attorney General Jeff Sessions fired former FBI Deputy Director Andrew McCabe late Friday, and Trump spent the weekend lashing out at special counsel Robert Mueller's team and former FBI Director James Comey. Lawmakers, including several high-profile Republicans, called on Sunday for Trump to allow Mueller to continue his investigation, despite signs from Trump that he might take steps to end the probe.

"As I said before, if he tried to do that, that would be the beginning of the end of his presidency," South Carolina Republican Sen . Lindsey Graham said on CNN's "State of the Union ."

Anti-sex trafficking bill vote

The Senate will vote this week on the Stop Enabling Sex Traffickers Act, an anti-trafficking bill that would allow victims of sex trafficking to sue the online platforms that facilitated their abuse.

Although it has overwhelming support from members of both parties, as well as anti-trafficking advocates and victims, there is some concern, particularly from tech advocacy groups, that it could limit free speech on the internet.

A senior GOP aide tells CNN that it is possible the legislation could pass Tuesday, though that timing will become clearer after lawmakers return to town.

The legislation would amend section 230 of the Communications Decency Act of 1996, which protects online platforms from content posted by third parties on their site.

While the provision contributed to the extraordinary growth of former start-ups like Facebook and Google, the freedom from liability has become particularly problematic in the instance of classified-ads style websites like Backpage.com. According to Shared Hope International, a nonprofit group that fights sex trafficking, Backpage.com is involved in more than 75% of online trafficking reports it receives from the public.

The new bipartisan measure, spearheaded by Ohio Republican Sen. Rob Portman, would give victims the opportunity to take legal action against websites that hosted ads that led to their victimization. Some tech advocacy groups are concerned the proposed change could stunt Internet growth and particularly affect small start-ups, which would not be able to bear the weight of potentially costly lawsuits.

The bill's House version passed with overwhelming majorities from both parties, and with 68 co-sponsors in the Senate, the legislation is expected to pass that chamber.

Yemen and war powers vote

The Senate is expected to debate a war powers resolution this week that calls for the United States to end its involvement in the Yemen conflict, but a top Senate Republican, Whip John Cornyn of Texas, said GOP leaders would prefer to put off a final vote on the divisive issue until after it can be more closely studied in committee.

The US has provided military support -- including intelligence sharing, logistical support, and mid-flight refueling -- to a coalition led by Saudi Arabia against Iranian-backed Houthis in Yemen. The conflict, which is considered, in part, a proxy war between Saudi Arabia and Iran as they struggle for dominance in the region, has created a dire humanitarian crisis in Yemen.

Three senators -- Utah Republican Mike Lee, Vermont independent Bernie Sanders and Connecticut Democrat Chris Murphy -- authored the privileged resolution and are working to force a vote on it. They believe the refueling and other actions by the US armed forces are akin to "boots on the ground" and that Congress needs to authorize those activities.

Pentagon leaders oppose the resolution and have argued that such limited assistance they are providing doesn't constitute "hostilities" that need congressional approval.

Senators and aides involved in the issue say they are unsure where the votes are and predict it could be close. GOP leaders may try to redirect the measure on procedural motion, for which a majority vote is needed to succeed.

Such a move could diffuse the issue, which is set for debate as Saudi Crown Prince Mohammed bin Salman visits Washington this week.

Cabinet members on the Hill

More of the President's Cabinet will trek to Capitol Hill this week to testify on their respective agency's budgets, but expect some to face tough questions over lavish spending and public missteps. Embattled Housing and Urban Development Secretary Ben Carson will appear before both House and Senate committees and will face new questions about his and his wife's involvement over a $31,000 furniture set purchased -- and then canceled following news reports -- for his office.

Education Secretary Betsy DeVos is also expected to face a grilling at a House Appropriations hearing after a series of interviews in which she couldn't answer basic questions about the country's schools, admitted that she intentionally had not visited underperforming schools and diverged with the White House by saying that "everything is on the table" over school safety measures, despite the administration's proposal excluded raising the legal age to purchase firearms from 18 to 21.

And Veterans' Affairs Secretary David Shulkin -- whom White House press secretary Sarah Sanders suggested last week might not have the White House's full support -- will testify before a Senate committee. Appearing before the House last week, Shulkin tried to diffuse a flurry of news stories about his agency, saying he "deeply regrets" the "distraction" at the VA, but is still expected to face tough questions over over a damning inspector general report that implicated both him and his senior aides on the costs of a 2017 trip to Europe at taxpayer expense.

Other Cabinet officials expected on the Hill this week include Agriculture Secretary Sonny Purdue, Energy Secretary Rick Perry -- who has dismissed rumors of replacing Shulkin at Veterans Affairs, saying "I've got the perfect job" -- and Commerce Secretary Wilbur Ross. Finally, Kevin Hassett, Chairman of the Council of Economic Advisers, will appear before the Senate Budget Committee to deliver the President's economic report.

Gun march Saturday

Saturday could bring as many as 500,000 people to downtown Washington for the March For Our Lives anti-gun violence rally. The organizers are students who survived the shooting at Marjory Stoneman Douglas High School, which left 17 people dead

The march is scheduled to begin at noon on Pennsylvania Avenue, between 3rd and 12th streets NW, though organizers expect participants will start to gather several hours earlier.

Parkland students raised $3.7 million in just three days for the march, and Oprah Winfrey, George Clooney and Steven Spielberg are among the donors. Celebrities Ariana Grande, Jennifer Hudson, Miley Cyrus and Demi Lovato are scheduled to attend the event.

The approved permit for the march included the use of 14 jumbotrons, 2,000 chairs and 2,000 portable restrooms, The Washington Post reported . More than 750 "sibling marches" are also being planned around the world that day, according to the event's website.

It's not clear how many lawmakers will attend the rally, as Congress is expected to begin a two-week recess surrounding the Easter holiday after it passes legislation to keep the government running. Congress has not yet been able to send any legislation to the President in response to the Parkland shooting, though it's possible that some narrow legislation -- such as money for school safety or incentives to improve reporting to the national background system -- could be included in the omnibus spending bill to keep the government open.

Miscellaneous

Lawmakers from both parties are likely to pay tribute to Democratic Rep. Louise Slaughter of New York, who died at age 88 last Friday . She was one of the longest-serving members, and well respected for a career championing her party's agenda that included becoming first woman to chair the House Rules Committee.

The House will also vote on the so-called "Right to Try" bill, a measure that would allow terminally ill patients to use drug therapies that have not yet been approved by Food and Drug Administration. The bill failed to pass the chamber last week after Republicans scheduled it on the House floor under a procedure requiring two thirds majority to pass and a large block of Democrats opposed it, arguing it didn't protect patients' rights.

The House Energy and Commerce continues its focus on combating the opioid crisis with two hearings over three days to advance more than two dozen bills.

The acting administrator of the Drug Enforcement Administration, Robert Patterson, will face some tough questions about the agency's policies and what led to the distribution of massive amounts of prescription medications to small pharmacies in West Virginia serving tiny populations.

And ending things on a lighter note, fans of the FX drama "The Americans" should set their sites on Capitol Hill this week.

The cast and crew -- including actors Matthew Rhys, Keri Russell, Noah Emmerich and Holly Taylor, as well as show creator Joe Weisberg and executive producer Joel Fields -- will join the House Creative Rights Caucus for a panel about copyright protection and the contribution of the creative arts industries to the national economy.