If the gasket leaks at all it need a shave, called resurfacing, which requires removal of the valves. This happened on my '98 and I have to replace the cooland temperature sensor on the exhaust manifold just to the passenger side of the fuel rail, ir began to short for some reason. $15 fix. I also ended up having to run Prestone Super Radiator Cleaner, which was an epic fix, my coolant system is perfectly clean now. The temperature doesn't even wiggle anymore after warming. Tthe Prestone is a $7 product, and cleaned out the fins on my radiator, which were getting clogged. Try those fixes before you unload tons of money at it. I reccomend this assuming your fans are working and you are not dealing with a full-on overheat problem. The heater controlling the temperature suggests that no one part of the coolant system is failing completely.