Im confused, how would you not know the car had a blown head gasket? Just look in the engine bay, under the car ect. thats pretty much #1 when buying a car. Also on a high mileage car, always do a compression test, no matter how it runs.
But you did get a good deal regardles if it has issues, I bought my ZX3 with 165k on it for 1500 and it needed a valve cover gasket and the shift cables broke on my twice.