jhigbee - sorry to hear this happened. I would first call a lawyer, and explain what happened. Most lawyers will listed and advise on your legal rights.
Assuming you have none, I would get a price for the repair, and contact the dealer (GM as the salesman cant do anything) and request they fix it. If they dont (which they wont) you need to figure out what you can get them to pay for. Most of the time they will pick up something to save face, and avoid a law suit. You might be able to talk them into doing the labor to replace the tranny if you provide the part. This costs them at most a few hundred in labor to the tech, and allows them to save face.
Good luck