You can charge for your services. Most I know charge around $20/hour for services. I personally don't do much and when I do it is normally on a friends gun and it gets done for free. You get a price list on stuff from Glock and can charge whatever the market will allow for them. I dont carry insurance as I don't do modifications to the frame, slide or barrel. Just diagnose, and replace parts.
If you want to advertise I would say get in good with a couple of local gun shops and leave business cards with them. Go talk to CLEOs that use Glock they may or may not have a armorer on staff.
If you want to advertise I would say get in good with a couple of local gun shops and leave business cards with them. Go talk to CLEOs that use Glock they may or may not have a armorer on staff.