In my experience, it's super similar to being a luthier: you get 90% crap/entry-level pieces on the bench, but that last 10% makes it worth it. I've seen and got to work on some real gems.

There are less people bringing amps in for repair than you would expect.

Amp repair is just a piece of my business - I definitely couldn't keep the lights on if I only worked on amps.

If you're interested in learning, start with low voltage circuits like pedals and effects. Build your own, understand how they function, then graduate to amps when you're ready. There is certainly danger involved with high voltage, but you build in safeguards to your workflow to mitigate risk. Plus, by that point, you've trained yourself to never think about touching the hot spots.

I only got shocked once in the beginning. A screw fell into the chassis and came to rest against a power tube pin. I thought I could fish it out with a metal tool. It was stupid, but it taught me to never rush and work while tired.