It's not going to work. You're going to find that out about 5 minutes into making your first change, that you can't do it. Mostly because even if you DO somehow manage to seamlessly edit out all mentions and foreshadowings of Anakin's transformation into Vader--Ben still gives it all away in Episode IV. The surprise is dead right there.

That's not taking into account how hard it's going to be for you to chop out all the "Birth of Vader" sequences from the climax and not make it look and sound like crap. I'm sure you could technically DO IT, but it would be nigh unwatchable. You can't "Fix" the Prequel Trilogy to ensure the twist in ESB is perserved. The only way that twist stays preserved now is to show them in release order, to someone younger than 10, who hasn't heard the secret in a joke or on the playground. Other than that, you're lost.