I was 24 when I went back to school. The only suggestion I have is to pick something that you are interested in. Don't just go into something that pays well. Good luck.
Check into going to a community college. Take a night class and really dedicate yourself to getting an A. Then take another class the next semester. I guarantee you if you do well, you will be able to get into a program somewhere.
But you have to prove to them through your grades that you can do the work and that your criminal background is no longer a fair representation of your current self.
I come from a construction family on all sides. I'd switch jobs if I were you, or take a masonry class or something at night so you can go from contract labor up to mason. Lot of brick work around here, and probably where you are too.