Petrov suffered the agony of losing the 2003 UEFA Cup final to Porto in Seville when he played under O'Neill at Celtic and experienced bad dreams about the setback.
Now he wants to lead Villa to their first major silverware since they overcame Leeds 3-0 in the 1996 League Cup final - two years after defeating United 3-1 to also lift the trophy.
Midfielder Petrov said: "This is the biggest day of my club career. We are heading for a massive game for this club, for the players, for the fans and I hope at the end of it we can all be happy.
"But we don't just want to be passengers there, just to go and enjoy it, without winning it. We will put up a massive fight and we will do our best to win it.
"The only way you enjoy it is by winning. I have been there with Celtic and I know how it is when you lose.
"When I lost in Seville, people said to me 'at least you went and enjoyed it'. That just wasn't the case.
"To be honest, I was still having bad dreams about it nights afterwards.
"I was so close but we just couldn't do it. Now we will put every single power and energy we've got into trying to lift this cup for Villa."
Agbonlahor, Milner and Young are all still in contention to be part of Fabio Capello's World Cup squad this summer.
And Petrov believes they will relish, rather than be fazed, by facing United in such a showpiece game.
He added: "We have young players but I am confident they won't freeze. We have players who have been dealing with the pressure for the last three or four years.
"They have become more mature players and they know that getting more tense won't get you anywhere. They are going to relax because we have so much talent here and we need to show that in the game.
"Villa are on the verge of something big - but it's up to us whether we can produce it. You're so close but you could end up with nothing and we don't want to be like that."
Left-back Stephen Warnock echoed the belief in the Villa squad they can topple the Red Devils.
He said: "People say we have a young team but there is quite a lot of experience within the team for such a young team. I don't think we really fear anyone.
"You fear losing the final more than anything because you'd do anything to win it and we know United are such a good team.
"But we know we've got the players capable of beating United and getting the right result. We've taken four points off them this season.
"It's whether we can do that on the day and how well United play.
"If they play to their potential, and everyone is firing on all cylinders, then we know it is going to be a very tough game."
O'Neill appears to have a virtual clean bill of health with Petrov winning his battle to overcome a virus which kept him out of the FA Cup fifth-round replay win over Crystal Palace in midweek.
Brad Friedel, James Collins and Emile Heskey, who were all rested for that game, will come back into contention to be part of the starting line-up at Wembley.