Grand Prize Chevrolet Buick GMC

I had a GM vehicle that broke down when my son was driving it. He towed it to the dealership he works at. My son is a "Master Guild Technician" Which is the highest rating a technician can obtain. My son pulled the valve cover off, (6 bolts) and discovered a broken timing chain. I called G.M. about this problem and I was told they would help with repairs, even though the car was off warranty, however, the car repairs must be done at a G.M. dealership. The car was towed to Grand Prize. I was told by the service writer, there would be a $250.00 diagnosis fee. All they had to do is OPEN the hood. The problem was RIGHT THERE, in front of them. When the service manager found out my son took the valve cover off, he refused to work on it at all. The service manager also said that GM would NOT help with the repairs, when GM clearly told me they would. I will NEVER, EVER take a car there for service, or repair. I would suggest everyone NOT go to Grand Prize Chevrolet in Nanuet for their service or repairs.