I won't be any help on the tech schools as I'm not familiar with any of them. But I agree with Rails that you will need that first big break to get in the door of a shop then prove yourself.
I've no training in the automotive field, but I grew up with a wrench in my hand. Just doing work on the family cars and some friends cars since I was about 10. My first car I bought for $125.00 put in a timing chain and sealed up the engine. Years ago I got the chance to work for a small, respected shop where I got one on one OTJ training from a very talented mechanic, welder, racer, fabricator, yada.. yada... That job lead me to where I am today.
Just be sure that turning wrenches is something you really want to pursue before jumping into to it, I know that if I was still doing repetitive repairs, warranty work and basic service work I'd go nuts. Also tools will be a major investment. As for the computer side it will help if you have a high reading comprehension and it still requires alot of grease monkey work. Mechanical problems can cause computer problems and computer problems can cause mechanical problems.
A few years ago a guy showed up looking for work, he spoke for a few mins with the boss and then they walked out to his car. A short time later my boss returned and I asked him about the guy and here is what he said, "I told him that once he got a bigger tackle box to come back and try again."
Fast enough 2 get by.....old enough 2 know what not 2 try -You know it was me