Career Path: Auto Tech, Diesel Mechanic, Motorcycle Mechanic? Your thoughts.

I know these are three pretty different areas, but I would like your
thoughts.

Here's my situation (briefly): I wanted to be a mechanic in 3rd grade.
Instead I went to college, got the degree, wandered around for 10
years, and now I'm realizing what I really want to do: work with my
hands fixing things.

Auto tech seems good because cars are everywhere.

Diesel tech seems good because I think of it as commerical fleet
oriented.  Not too much customer B.S.  Plus I like diesels.

Motorcycles because I can get big tattoos and sound tough in bars.

What do I need to know that I don't?  I know my way around a car but
am not a shade tree mechanic.  I'm not looking to make lots of money. 
I'm just tired of doing desk jobs I hate.

This is a tough, open-ended question.  Any comments, ideas, flames,
etc. are appreciated.

Harris