Can I make a suggestion here? You need to think about who and what you are already. Specifically, you need two different mindsets going in:
1) The "troubleshooter gene": somebody who can see something mechanical and figure out how it's supposed to work and why it's not working. If you're already competent at fixing bicycles, cars, motorcycles, etc. you're probably good to go.
2) You ALSO need the "artisan gene": the ability to be a perfectionist in making it not just work right, but look right. Typical example is the guy who re-finishes an old desk or other furniture and it comes out looking superb through painstaking effort.
I personally have number one but not number two. I would never work on somebody else's gun unless it was an emergency and he had to get it running, in which case I'd take my best shot if there was nobody else...wilderness survival situation, post-SHTF, whatever
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If you don't have both of these genes together...yeah...sorry, but...don't even bother
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If you DO, by all means! We need you.
OK?