Body Shop Info
I would recommend the following (I'm an Independent Collision Repair Shop Owner):
I agree with the latter, if you have a MB shop (dealer owned) that would be a good bet provided they are certified by MB. Also check to see if they are certified as preferred shops by the major insurance companies (State Farm, Farmers, etc.). An independent shop would work just as well provided they have the same insurance certification.
Questions to ask:
1. Warranty - Labor, Parts, as well as paint.
2. Parts - Used, Aftermarket, or MB (be aware that most collision parts for MB (fenders, etc.) are made in the USA, so if your car was made in Germany, there may be fitting problems). Aftermarket parts are a way to save money, sometimes you get a good fit and other times you don't - I have had good and bad experiences with aftermarket. Used parts are a great savings and will provide good solid fits - make sure there is no rust.
I would definitely ask to see the shop itself - this will give an indication of how they will take care of your baby - dirty shop, dirty work.