Manifold and overheating on 2001 Oldsmobile Aurora

I took my Aurora in for overheating. The mechanic replaced the manifold at a cost of @ $1300.00, but it kept overheating every time I drove it. I asked if it could be the head gasket and they told me no they had tested that. Long story short and @ 9 weeks in the shop, still overheating. I took it somewhere else and it was the head gasket, failed test immediately. They told me manifold caused overheating is not a common problem with this model. Have you any incidents where this has been the cause of overheating in this type of vehicle? Could continued overheating caused further damage?

Asked by for the 2001 Oldsmobile Aurora
Continued driving the car with a mildly or seriously blown head gasket will only hasten more serious engine damage. The only two bulletins I see to do with overheating are an updated thermostat to improve flow and another bulletin speaks of mentions some radiators had a poor sealing surface between the radiator cap and radiator end tank.