Whatever you decide, be very very very very very VERY wary of For Profit "schools".
By and large, none of them are worth the money it takes to get a diploma from them. (this is also sage advice for anyone who may read this, not just those looking into auto / diesel tech)
My cousin was, for a short time, a diesel mechanic for Raisor Ford in Lafayette. I asked him where he got his schooling / training. He just told me that he got his training direct from the manufacturers. He only listed three: Cat(erpillar), Cummins, and Ford. He worked on road-going vehicles.
And, overall, he didn't do that job too terribly long before moving on/up to manage the shop at the Raisor PowerSports dealership.
That's not what most have told you at all. You will NOT get a job making the big money and working on the serious jobs for a looooong time unless you have formal training.
If you want to be doing brake jobs and changing shocks until you're 40, be my guest.
Then again, I don't turn wrenches anymore for a living, so perhaps my information is a bit dated. But having sold parts + turned wrenches for a few years, I can tell you that every shop has people who are good and get the good work and others who are crap.
Wyotech if you don't mind going out of state, Lincoln if you want to stay in-state. I don't think you'll have a difficult time finding a good job regardless. Congrats on being proactive!