I'd go after the dealership for wrong troubleshooting. The engine could have been saved, if they found the real problem and fixed it. Bad lifter, ok, change the lifter, maybe the camshaft, maybe something else, but not the entire engine. That's why you brought the car to them, to get it fixed, not just throw some parts at it, that was probably not needed, and now you have to pay for and then they turn the key, blow your engine and are telling you that it would have happened anyway. No! It would have not happened. They could have borescoped the cylinders, check the valve train, check compressions, ets. That engine could have been saved with minimal repairs.