You say you want to do this for a job...
Here's how you get that particular joy:
1. get one (mag, cocker, whatever. You sound like a kinesthetic learner)
2. get on the websites where people work on them (that Mag owners group, Ravi's homepage)
3. start screwin' around making a mess in your bedroom (got that technique down)
4. offer to help some store with it's overruns (they will need some reason to trust you- I leave that as an exercise for the student)
5. after a few of the gun owners getting hold of your phone number, you will be too busy to sleep. You tell them that fixing their marker the night before the tournament, when they call you at 10 is crossing a line beyond which you need to be paid
6. presto! plenty of cash and no time to play! you win!
Keep your skills as secret as possible. Same with the phone number.