What is the avrage cost of head gasket replacement

The cost of repair depends on what needs to be done . If you get it done at the dealers or a local shop . If you get it done right or half assed. the tear down and rebuild will take about 6 to 10 hrs the head gasket kit will cost roughly 100 for gaskets but you really should have the heads machined unless you want to do it again later. Then theres do you need to replace the bearings in the bottom end. if the head gasket had caused coolant to leak into the oil you will need to rebuild the bottom end . If your oil looks like chocolate milk dont risk it it will fail in short order.If the oil was contaminated I would look for another motor. It would likely be cheaper than the rebuild. So throwing a number out there would be hard 600 on the low end 2500 on the high end depending on what has to be done.