Thanks guys. Sounds like doing the work myself is way above my tech level, and takes much more time than I have. I'm going to try the lube guard and tranny flush first. But I think that may just be temporary. Probably gonna have to have the shop fix it. Yes, there are codes associated with it, I've pulled them a couple times. They indicate that the TCC solenoid is stuck, but the GM guy I got looking at it thinks it's the valve body. Anyway, I'll let you know what happens!
Thanks.