I'm 24, I work full time and just started school full time. Right now it's pretty manageable for me, but my job is pretty flexible and allows me the time to do school/hw.
you mentioned that you do a lot of OT, if you go to school full time I wouldn't count on OT for extra cash.
Trade school especially through a union sounds like a good option too.
I know a lot of union guys that do very well for themselves, I also know some who have a hard time getting work. Off hand I don't know many college grads that don't have jobs, but that doesn't mean they're better off than the union workers.
Whatever you do just make sure you're fully committed to it, otherwise it will just be a big waste of time and money.