First things first.......Welcome to the Werkz......second lets not jump to conclusions....
I would say from the sound of it, your thermostat is bad, first stuck open, explains why you had no heat, then sticking closed causing it to overheat.....also what is the mileage on the car.....? Is the original waterpump in the car? If so, they were known to have a plastic impeller that breaks apart due to poor design.......If I were you, I would just replace the coolant, thermostat & thermostat housing.....the stock housing is also plastic & recommended to replace with cast aluminum.....
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johnny,
A blown head gasket would be blowing out a lot of sweet smelling steam from the tail pipe......