I fix/repair/mod guitars! Yes, I do and have been doing it for over 10 years. There’s always something that needs fixing or adjusting on a guitar or bass. I have done it.
The oldest guitar worked on to date? A 1959/60 Fender Jazzmaster. I restored a poorly playing Jazzmaster and gave it a new life with updated Mastery bridge, new pickguard, new nut and Seymour Duncan pickups. (pics soon!)
The most complicated job? Trying to un-twist a neck! It took a lot of clamps, weights and hours of steam!
Other than that, a good fret job and intonation job does wonders for your guitar. Also, I swap in new pickups and electronics.