Echoing BikeWise1 ... some shops are well run, and some are not. One local shop (a shout out to Bike Source) always has at least one very good head mechanic on staff, and the other wrenches don't hesitate to escalate a weird part or repair request to him the moment they're stumped. At two other nearby shops you might get stuck with the expertise/competence of the first guy who comes to help you -- someone who would as soon guess at the part you need or do unneeded/unhelpful work and send you off before seeking help from a more knowledgeable staff member. I suspect these last two shops employ mechanics who are independent jobbers -- purely a guess, though.