I was initially a "self taught" mechanic, hung out with the wrench crowd and learned a few things between beers, gained enough confidence to tackle major repairs, but made my living with computers (small business/PC hardware/software/networking). Got my
A&P one year but the computer market had a lot more offers and pay (and less liability as TC notes), so I never actually used the A&P for a living, but learned quite a bit about things mechanical. Eventually went back for a comp-sci degree, I didn't learn much new in that exercise, just wanted a piece of paper with my name on it.