Wyotech is supposed to be one of the premier schools in the country. A buddy works there and has mentioned some fo the requirements to pass. Interesting tidbit, you'd be building a 4T65E and dyno testing it before you'll pass.
A friend is a mechanic and he owns his own shop. His advice to anyone thinking about it is, don't. You beat your body to make money and overall the working conditions aren't stellar. Breathing chemicals often, brake dust, rust, cuts, scrapes gouges, burns, dealing with rain and snow dripping off cars, heat in the summer. A good mechanic can struture things in the right place to make very good money. It's work though and like most things in life there is a downside.
