A gunsmith is basically a "metal smith" and a "wood smith" with an FFL (Federal Firearms License) or he/she is a crook...
You can teach youself with books from Brownells for your own amusement or you can find training in machine tool and wood working at most community colleges days? part time? Evenings? No, I doubt the community college will let you bring guns on campus, but they also have a "placement service" to help you find work. If this is for your own enlightenment, I would go the books route. A certificate from "Mail specialties" is worth??? If you are serious about full time, get the college paper and internships and
Your taxes at work... luck.