i'm gearing up to do my first home paint job in a couple weeks... about a year ago, a woman took out my driver's side fender, hood, bumper, and grille... etc. damage was primarily just sheetmetal... just enough to make it worth just getting new panels. anyways, i've been waiting for the right time to get the car back to one color... so, right now, the car is in primer on the hood, and driver's fender. the rest of the car is in marina blue metallic. i want to re-paint the entire car while i'm at it in a bc/cc. the painted part of the car has only one paint job on it, and it pretty damn straight.... it was totally stripped on the previous job. would it be acceptable for me to just sand down the paint a little, do any necessary bondo work, then prime the whole car? or is it mandatory to strip the whole thing down to metal? thanks.... sorry if this is a stupid question, but i figured better that i ask it than not be 100% sure on it.

You only need to "scuff" the good paint so the new paint will stick to it. Use wax & grease remover first to get all the wax off. If your already painted side has a little wave in it or a flaw block it out now.

Make sure you seal it too.

what grit would you guys recommend sanding with?

For the final wetsand before sealing it,I'd use either 600 or 800 grit.