Balco - I think that the key word in your question is "rewarding." Other trade jobs probably will pay more, maybe even much more. And they might be reasonably reliable. But you have to commute, maybe long distances, you can't control the noise, you might work for a jerk.
If you think you'll love gunsmithing, happiness in your work and with the people around you counts a lot. It is likely that in the process of gunsmithing you would pick up skills useful for side handyman work, and I'd imagine that from time to time you can come across some really good deals on purchases.
I'd balance that with the cost. If the gunsmithing school wants to finance your education with one of these loans that will haunt you forever, versus learning to be a plumber or electrician at the employer's expense, that is a huge difference. When a school says, "Don't worry about the tuition, we'll help you!", then I'd worry about the tuition.