I need to have the head gasket repaired on this car, and have received an estimate of over $1500, including over 10 hours of labor. I looked online and found that the part itself costs only $12-$55. (Car has 80000 miles) What is a reasonable charge to perform this repair?

The price may reflect machining charges for warped head and valves, due to overheating. Find out first before going ahead. It's not a bad price at all if machine work is required.