United have struggled to live up to their potential under van Gaal and failed to qualify for next season's Champions League after finishing fifth in the Premier League.
Van Gaal's job is under threat following two seasons of underachievement and the United manager was booed by fans as he addressed them after Tuesday's 3-1 win over Bournemouth at Old Trafford.
The Dutchman is keen to play down the impact a Cup final triumph at Wembley would have for his own future.
However, he feels it is time United ended a three-year trophy drought by winning the FA Cup for the first time since 2004.
“When you win silverware, it is always important. It's important for the players because qualification is not a title. A title is the FA Cup or the championship,” van Gaal told reporters on Thursday.
“For players, it is always very important, because they can look at and can hold a cup. That's an exciting moment also, especially here in England, because the FA Cup is a big title.
“We are playing in the most prestigious temple in England, so everything confirms how important this cup is.”
United's last silverware came in 2013, when they won the Premier League under Alex Ferguson and then the Community Shield under his successor David Moyes.
Van Gaal's failure to win a trophy so far, coupled with the availability of former Chelsea boss Jose Mourinho, has left United's board with a tough decision to make at the end of the season.
The current United chief has one year left to run on his contract, and hopes to see it out, but has slapped down speculation about his future.
“I think the interests of the club and the fans are much more important than the interests of the manager,” van Gaal said.
“Of course, you set your own aims, and that's one of the aims that I have always had. It's always exciting when you are so close, but close is not enough. You have to win it.
“A club like Manchester United need silverware. You have read that all season. We need that. The players need that also.
“That's why it's so good when we win, but we still have to beat Crystal Palace.
“That's not so easy. They have a lot of quality. They defend well, and they have a lot of speed on the counter attack, so it shall be very difficult.
“The most interesting point is that we are able to win something, and now we can win something. We are very close. But still you have nothing when you don't win.”
Van Gaal has warned of the threat that Palace will pose from set-pieces - from which they have scored a high number of goals this season.
“They have scored 29 of their 56 goals this season from set-pieces, so more than 50 per cent of their goals have come that way. That's a lot more than we have done,” he added. – AFP
Original source: Cup win will restore United’s pride - LVG