If they are lucky, enough to pay their bills and eat.
By hand
The colonial gun smiths took 1.1111 zillaseconds to smith a gun.
some did but some were brought over from Europe
Fix and/or repair
In the 1700-1800's guns were not made with interchangeable parts, so a gunsmith would have to charge according to the job he is asked to do. We can't give you a set price because each part or gun would be an individual job.
wood, iron, coal, anvil, hammer, draw file, draw plane, hand plane, hand file
Try e-gunparts.com, gun shows, gun shops, gun smiths.
No way to answer without knowing what make and model the gun is.
Smiths do not make gold, though they do manufacture items from it. Gold is a naturally occurring element.
Blue book of gun values
All metal and woodworking tools, including hand, power and machine tools.
black smiths make them