My suggestion on what to do with that car:
Keep it exactly the way it is if the engine and tranny is good. I would then fix the vert top so it's fully functional, remove any and all M3 badging, if the paint is going, I would get a quote to have that sick *** color resprayed (I love Techno Violet). After all of that is done, I would look into an M52B28 swap (2.8L L6).