The PCM should show some basic transmission codes.

You have a 6T70, so there are a number of possible causes for this. The most common are related to a 3-5-R wave plate failure. Sometimes it is bad or clogged solenoids.

A good shop will be able to diagnose and repair to some degree, but most any shop will probably not warranty anything besides an overhaul. If you're handy, willing to do the work, and understand automatic transmissions to some degree, you might be able to do some partial repairs.

Yeah i dont have the space nor the tools. I replaced my own front hubs and handy with mechanical. But just no way to get it out and work on it. I'll have to get it to a shop.

That'* probably a good idea. If it were one of those units where you could do more with it while it is in the car then you might have a shot at avoiding a shop. This one you have to drop it out for just about everything.

Yep, engine and transmission all in the engine compartment.