Wow, what a crappy situation! I'd say deal directly with the owner if the GM is giving you crap. If you were prepping for that kind of higher end detailing have the people that looked at the car talk to them.
At this point if they are complaining about door dings that's ludicrous. They're the ones that damaged the car allegedly and painted it poorly without your consent. A few hundred dollars in PDR work shouldn't be something they are arguing with you over.
I hate to say it but this is sounding more and more like a situation where you won't walk away satisfied. I'd really consider hiring a lawyer outright and sitting down and having a conversation with the owner of the shop with your lawyer present.
I believe that it's entirely possible that they could make it right and do a good enough job to make the car as good or better as it was, but this is a really ugly situation, and having been through similar problems twice I'd say it won't end well.
When I was in HS my Mom was shopping for a new car and the dealership had a decent Chevy Blazer with a reasonable amount of mileage that was in my Mom's price range but the paint was shot. It had a little bit of surface rust on the lower rockers, etc and the clearcoat was faded.
The dealer made the offer to my Mom that they would do a full paint job on the car in an effort to sell it and get her the vehicle she was looking for.
Sounds like a great deal if the paint job was up to your expectations right? It wasn't. And by this point she had already signed for it. They completely neglected to paint it below the lower door/upper rocker rubber trim, under the bumpers, etc. A "full respray" to me is a FULL RESPRAY. As in take the bumpers off, take the trim off, do a complete job. We gave it back to them twice. The first time because they didn't do the rockers, the second time because even after I complained that they didn't touch the rockers they didn't take off the bumpers and I could see rust behind that.
After the 3rd trip to a body shop (and finally a different, more competent one) they finally gave up. They appologized for the whole thing and offered to buy the car back and get us something else of equal value.
The problem was finding that, and getting them to agree to pay for it. My Mom wanted a 4WD Blazer with under 70K miles. They kept saying they couldn't find one that met her criteria, and then they started offering other completely different cars. Like a 4 door Olds Cutlass. I finally told her just take whatever damn car they will give you because it had been 8 or 9 months by this point. In the end a year later they finally stopped talking to us and she just gave up.
I'm afraid that your insistence on a black S2K with an equal or lesser mileage range is going to get the same result. If I were you I would tell them you want the book value + 1 or 2 grand for your hassle and ultimately your silence on the whole matter. Your expectations may be too high, their willingness to try and spend the time and money to make the car PERFECT may be low, they may eventually get aggrevated with you in the whole process (even though you have every right to be angry and demand a proper fix)and the whole situation could degrade.
IMO having them pay you the book value of the car would be the best outcome. Then they own the car and they can decide how much effort they want to spend on fixing the car and selling it to someone else. Hell they may even find that fixing the worst problem areas with a slightly less half assed paint job and less investment in time and labor on their part they could sell that car for $12K to someone with lower standards. Maybe even someone that wants nothing more then a track car for a good price.