Thanks, I've been at it for years and years, and very rarely let anyone else "fix" my guitars. I found out long ago I can do a much better job than 90% of them, and have the tools because I was once a machinist for 8 years and have always tried to pick up anything that might work for guitar maintenance/repairs. Plus I'm just a tool junkie anyway, it's almost as bad as the dreaded Guitar Acquisition Syndrome... Got the 24" machinist rule a year ago or so at a local auction, $3 for a box of stuff, the $35 (or more) Starrett was the only thing in the box I wanted...
A lot of the info I've picked up also comes from research, especially online. A number of luthiers have set up websites with excellent instructions for doing just about anything to a guitar you might think up.
Frets is one of the best. I got the idea for my fret crowning file from a friend locally who repairs guitars, since actual fret files cost a lot of bucks, he ground the corners off a small triangular file and uses that. He's also the one who turned me on to foam fingernail files for buffing. I've been amazed how well they work.
One thing I forgot, you can use a 6" or 12" ruler over short areas and check to see if it rocks back and forth over a fret. That's useful if a high fret isn't very visible.
Gunsmithing is another area I've tinkered with but not as heavily as guitar repair. Mostly minor stuff, and learned as a kid how to disassemble and clean every gun in the house, that was my chore after we came in from the woods. No nap, no go outside and be a KID...I had to clean the guns...I can take a Winchester Model 12 down, clean and reassemble blindfolded...I did it once with my eyes closed just to prove it to myself, my father never knew the next time he took it out I had no idea if it was actually right, I just knew it would shift shells through properly. I did look to make sure the barrel was clean, but that's the only time I peeked. I didn't get my ass beat so I guess it worked fine...He took it duck hunting once with his brothers and it was the only shotgun that was usable, everything else froze and wouldn't shoot, all automatics. He had to break the ice off his model 12 every time, but it would still fire...
Yes I also clean and repair all my fishing reels, I've been reworking Ambassadeurs since I was 10, guns before that. Rebuilt the engine in my Jeep myself too...(but that was only a year ago...) I'm partial to Ruger if you're talking pistols...can't beat a good Single Six for a .22
I have one gun I won't fool with now, an early 1900's H&R long tom 32" barrel with broken hammer tang and loose pivot pin. (last patent date stamped on it is 1905 or 1907) Kicks like a mule and throws buckshot way out there...but I never fire it any more because the pivot pin is loose - it's dangerous, so it's now a wall hanger. I'm not good enough with firearm repair to do it myself and don't trust most shops. After a local amp tech swapped out my tubes for old weak ones, I avoid letting anyone else work on any of my stuff. Right now I dont have the $75 or so to replace a quad of 6L6's...the amp sounds weak and wimpy, and that's my clean amp. I could handle it much easier if it were the Super Reverb, since the MX will do everything but the cranked tube amp sound the Super does so well. The MX is all about cleans...no breakup at all, even at really LOUD volumes... But nooooooo...the guy had to swap tubes in the MX...He'll never touch another of my amps...