Manchester United expect Louis van Gaal to win the Premier League title next season and have given their new manager a £150m transfer fund to rebuild the squad this summer.

Holland's current head coach is to be unveiled at Old Trafford in July after he has taken his country to the World Cup and before United's summer tour of the US, but on a dramatic day for the 20-times champions it also emerged that:

• Ryan Giggs is to be Van Gaal's No2 but he has retired from playing after a glittering career spanning 23 seasons

• Paul Scholes, Phil Neville and Nicky Butt have been left in the dark about their futures on the backroom staff

• United began speaking to Van Gaal just 48 hours after David Moyes' sacking in April

Van Gaal has been challenged to win United a 21st title in his first season with the vice-chairman, Ed Woodward, sanctioning a sizeable kitty to pursue targets that include Southampton's Luke Shaw, Bayern Munich's Arjen Robben and Toni Kroos, and Borussia Dortmund's Mats Hummels.

Following the dismal championship defence under Moyes that ended with United in seventh place, Van Gaal is confident he can again make the club serious challengers as the business end of next season is entered, with a Champions League berth the very least required. Van Gaal has previously won titles at Ajax, Barcelona, AZ Alkmaar and Bayern Munich, having also won the European Cup with Ajax.

He said: "It was always a wish for me to work in the Premier League. To work as a manager for Manchester United, the biggest club in the world, makes me very proud. I have managed in games at Old Trafford before and know what an incredible arena Old Trafford is and how passionate and knowledgeable the fans are. This club has big ambitions; I too have big ambitions. Together I'm sure we will make history."

Louis van Gaal said he was very proud to join Manchester United and he had always wished to work in the Premier League. Photograph: United Photos / Reuters/Reuters

Later he told the Dutch TV station RTL that one of the reasons he was chosen by United was for his record in working with young players but he added: "The aim is to bring them back to the No1 position as soon as possible, because that's where they were under Sir Alex Ferguson."

Woodward said: "In Louis van Gaal, we have secured the services of one of the outstanding managers in the game today. He has achieved many things in his career to date and Old Trafford provides him with a fitting stage on which to write new chapters in the Manchester United story.

"His track-record of success in winning leagues and cups across Europe throughout his career makes him the perfect choice for us. People know him as a larger-than-life character but I have also been extremely impressed by his intelligence, thoughtful approach to the role and his diligence."

The executive co-chairman, Joel Glazer, said: "I am delighted that Louis will be our next manager. He has an outstanding pedigree as a coach, both as a man who motivates his teams to win trophies and as someone who believes in giving young players a chance to prove their worth."

There was a welcome from one of his main rivals next season in the form of José Mourinho, whom Van Gaal appointed as his assistant at Barcelona. "He is a great football manager and I am happy he joins me in the same country and the Premier League," the Chelsea manager said. "But more important than that, he's a great guy, a great man, and I wish him well."

Van Gaal said one of the first congratulatory text messages he received was from Mourinho. "He said he was jealous of my list of clubs," the Dutchman reported.

As Moyes was sacked on 22 April it took United four weeks to land Van Gaal yet the 62-year-old was always the No1 choice, having been first sounded out as the prospective new manager two days after the Scot's sacking.

The delay is understood to have been due to United wishing to respect his current employer, the Dutch Football Association.

There was also the future of Giggs to consider but once it became clear that Van Gaal would offer the Welshman the role as his No2, the Dutchman accepted after a meeting in Noordwijk last week. That is thought to have been the third face-to-face encounter between Woodward and Van Gaal, with Woodward "delighted" that the 40-year-old Giggs will remain on the coaching staff.

He said: "I am thrilled to have the chance to serve as assistant manager. Louis van Gaal is a world-class coach and I know I will learn a lot about coaching from being able to observe and contribute at such close quarters.

"Manchester United has been a huge part of my life and I'm delighted to be able to continue that relationship in such a key role."

Although Marcel Bout and Frans Hoek are also joining Van Gaal's coaching team – the latter appointment as goalkeeping coach, so Chris Woods departs – the futures of Scholes, Butt and Neville are still to be decided.

United consider the three members of the Class of 92 to be of great value to the club, though none of them have as yet been offered a role.

In an open letter published on the club's website, Giggs said of his retirement: "For me today is a new chapter filled with many emotions – immense pride, sadness, but most of all, excitement towards the future. United fans I hope will share and echo my belief that the club, the management and owners, are doing everything they can to return this great club to where it belongs, and I hope to be there every step of the way."