Ronni Bicakson does outstanding work. Among the very best.
http://www.nightowlpipeworks.com/
Mark Tinsky also does pipe repairs. Personally, I would not give a pipe to a shop to repair. In all likelihood they don't do it themselves, but farm it out to someone who you don't know. I'd prefer to send it to a pro that I know, or have strong recommendations of from other pipe smokers.