the more you drive it, the more damage you do to the motor. you need a shop to do a leak down test to confirm the number of cylinders effected by the failure. then they can give you a bid based on ther results. then after this is done, they need to find the original issue as to why it overheated. the head gaskets are a result of the overheating not the reason for overheating.
it will be costly to the point that it may require a new or rebuilt motor.