* Dutchman given three-year contract * Giggs to be his assistant (Adds background) By Martyn Herman LONDON, May 19 (Reuters) - Manchester United returned to a tried and trusted trophy winner after an ill-fated adventure with David Moyes when announcing that Dutchman Louis van Gaal had been handed the job of reviving the club's fortunes on Monday. The 62-year-old, who has masterminded league titles at some of Europe's biggest clubs including Barcelona and Bayern Munich, and won the Champions League with Ajax Amsterdam, will begin the re-building job at Old Trafford once he has finished national duties at the World Cup. Ryan Giggs, United's record appearance maker, will work alongside him after his four-game stint in charge following the sacking last month of Moyes, given the chance on the back of a long and worthy, but success-starved, 11-year stint in charge of Everton. "In Louis van Gaal, we have secured the services of one of the outstanding managers in the game today, United executive vice-chairman Ed Woodward said in a statement that announced the Dutchman had signed a three-year contract and would start work after leading the Netherlands in the World Cup finals. More...