I'm not sure on the prices for paint at bellows but I'm pretty sure that it's $40 and up according to what I last heard, I could totally be wrong though.
You could always visit the other fields that aren't FPO. There's an awsome field that was recently put up at Wheeler AFB, BYOP.
and installing your reg wont be a problem, there are several shops here and I'm sure they all can properly screw your reg back on.
The barrel you use is only as good as the paint you shoot.©
Disclaimer: I speak only for myself and myself only, and never for my team.