What are you trying to have done? Parts replaced? Cerkote? There are a number of them, 4 seasons has a certified block armorer for parts replacement, business end customs can do it as well, those are 2.
if you have a beat up glock, forget sending it out. Take it to a local smith with experiance like Lou, keep your money local and get what you want. Tell lou what you want the gun to do and how you want it to look. he does great work from what i have seen! i hope to get out that way some time soon to get my M&P45 tuned up by Lou.
I agree with spending money locally. Except that in the case of a glock, the factory will completely refurb the gun for FREE. All they charge for is if you want the slide refinished. Everything else is no charge.