Has anyone had problems with blown head gaskets,&how much more damage could be done to it if you drive it with a blown gasket.lets say 500mi

Bad idea. Continuing to drive it could easily cause major damage to the engine, transmission, and radiator.

I'm helping a single mother of two rebuild a 2000 Honda Civic LX, which was driven after it started to overheat. A local mechanic wanted $3,200 to repair the head, replace the timing belt, and water pump. The potential damage to your diesel could far eclipse this situation. My advice is to get it fixed properly ASAP.