I'd guess a grand, maybe more. The gasket isn't pricey, but getting at it takes a few hours. So it'll mostly be labor you're paying for. It all depends on where you live and who you have to do the repair. Replacing a head gasket is a major repair, even though the gasket itself is relatively inexpensive. Replacing this will also require replacing other gaskets. Labor costs vary greatly from area to area. In my area of the country, using a good independent shop, this repair would run around $500. It would be much higher at a Ford dealership.