I had an OE paint job done on my m3. It basically cost me a very good amount, i had one very small rust spot which had not spread it was cosmetic. I had chips etc etc.The color is Titanium silver, i had both bumpers painted, all new moldings. I would say you may expect a bill of around 3-6G's depending on the quality and the amount of repair needed.
I would also talk to philsans on this forum, he is located in Mass. From what i have heard from the other members of this forum, he is THE guy to go to.
Good luck.