A member of the first Barcelona team to win the European Cup with a 1-0 victory over Sampdoria 17 years ago at Wembley, Guardiola has led the Catalan outfit to a Primera Liga and Copa del Rey double in his first season at the helm.
He will now attempt to earn a place on the privileged list of five men who have won the European trophy as both player and coach.
Guardiola will also attempt to help Barca become the first Spanish treble winners with a victory in Rome.
"I could never have imagined anything like this at the beginning of the season," said the 38-year-old.
"I just wanted to do a good job, but in my first year to win the League, the cup and to be here, one step away from being European champions, is great.
"We cannot deny that it has been a great season.
"I have been fortunate to have a great team and we've been able to do well.
"But we can still do better."
Guardiola knows Manchester United have few weaknesses.
Sir Alex Ferguson's team go into the clash on a record 25-match unbeaten run in the competition.
United have a superb defensive record in this season's competition with just six goals conceded, but Guardiola is respectful of the whole team.
"I think Manchester United have lots of virtues," he said. "If we are not strong in defence they will attack and it is a team that attacks well.
"If it has to defend, it defends with humility and if it has to counter-attack, they are deadly.
Barca will rely on the inspiration of Spanish internationals Xavi and Andres Iniesta in midfield, while they hope Lionel Messi can maintain his form in front of goal.
Messi is the competition's top scorer with eight goals this season.
"We are going to see a great Messi," said Guardiola. "He is in good form and the team will help him to deliver.
"If we play in the way we can play, then Messi will have a good game."
Much of the focus has been on Messi and Cristiano Ronaldo but Guardiola feels any player could decide the game.
Barcelona last won the Champions League three years ago when beating Arsenal in the final in Paris with defender Julian Belletti scoring the winner.
"I don't know if the game will be decided by star players," Guardiola said. "Of course, because they are stars they have more responsibility.
"Both (Messi and Cristiano Ronaldo) are very good players."
Guardiola has remained tight-lipped on whether Thierry Henry or Iniesta will play.
Both have been sidelined since the beginning of the month through injury but are fighting against the clock to earn a place in the starting XI.
"We still have one training session," said Guardiola. "We will see what their condition is.
"If they are well, they will play.