You want to find one of the best body shop's period. BMW's metal and paint don't require anything that most body shop's don't have.
When my dad had to have some body work done on his 04' Infiniti G35, he took it to this body shop called: Sunrise Paint and Body. They were recomended by many luxury car dealers in the Houston Area. He was referred to them by South West Infiniti. They did a great job on it and since then they have done some work on my car (Acura Rsx). It also looks good and everything was fixed right. Heres a link to there web site: http://sunrisepb.com/default.htm
