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.
Yes, to make the name Smiths into the possessive form, add an apostrophe: 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.
All metal and woodworking tools, including hand, power and machine tools.
Blue book of gun values