I've always been interested in mechanical things and how things work. My Grandfather was a sewing machine repairman who worked in clothing and shoe factories. Those are long gone, but I remember watching him fix things in his shop. He lived to be 91 and was always the fixit man in our family. My Father had NO mechanical ability, which may have made it better since if I wanted to know how something worked I had to find out myself. I spent much time in the library reading books on engines, cars and anything else that interested me.
When I buy a car or bike, I always get a Haynes or Clymer manual (or both). I have been driving since 1977 and have never paid for a car repair in that time. And I have owned some real junk! If the car is not under warranty I repair it myself. Unfortunately, as time goes on I find it harder to get up and down from the ground, but I can afford to drive newer and better cars. I must admit that I have had a few exhaust systems replaced, but since it would cost the same and is such a pain in the rear, I don't consider it cheating. I could do it myself, but why bother?!
Being an apprentice in a bike shop sounds like a great way to learn, but in the U.S. there is probably some government safety restriction or insurance problem that would prohibit it.