I'm gonna cap off my advice with something that isn't really all that popular, so take it with a grain of salt.
Use some of your next re-enlistment bonus at AGI. Their master gunsmith course comes with a machine ship course and a welding course, all on DVD.
The gunsmith course will cover a lot of theory, but you won't get any hands-on. That's what volunteering at a local gunsmith shop will do for you.
The machine shop & welding courses, you can get the hands-on right there on the USS Bush.
Wish you luck.
No, actually what I really wish is that I had the gunsmith bug back when I was still in the Navy, and I still had all those things at my fingertips.
Best of luck,