Might depend on what you mean by "gunsmith." The natives learned pretty quickly how to fit spare parts onto a broken lock and how to restock a gun - little caches of lock parts and files show up in archeology from time to time dating as far back as the 17th century, IIRC. Hamilton's book on frontier guns has illustrations of some of these.
Harder stuff, like forging out new lock parts, rebreeching and refreshing barrels, not to mention building a new gun from parts, seems to have been largely the domain of whites. The French sent gunsmiths out to the frontier to do these kinds of tasks, which suggests that the natives couldn't do them themselves.
I do recall reading something about a late 18th-early 19th century gunsmith among one of the SE peoples, but I can't remember any details or where I read it, despite having tried ever since this thread was started....