If a color change it what you want....then the door jambs, underhood and trunk are not that bad, its the engine bay (for me at least) thats the killer. Depending on what color your car origninally is, you might get away with not spraying it. All up to you. But it is a BIG task to do a complete respray.
Same as the rest, scuff them up and clean them, as that is where a lot of dirt and grime will hold up in. Then paint make sure the jambs .etc are clean.