That sucks dude. I wouldn't consider that friend a friend anymore if he recommended a shop for your Z that does poor work and abuses a customer's car
It also sounds like you dealt directly with the other person's insurance company. I always file a claim with my own insurance company and let them deal with the other person's insurance. When I file a claim through my own insurance, they are the one who pays the body shop. So if I'm not satisfied with the work, I can inform my insurance company who will deal with the body shop. I can choose to have them fix the work, or I can go to a different shop altogether. Either way, the insurance company goes to bat for me against the shop that screwed up.