Before doing any work on the cooling system make sure the car is not hot and the cooling system is not under pressure. You have to remove the top thermostat housing to change the thermostat. The housing is bolted down with two 13mm bolts. With the thermostat housing off you will see the thermostat sitting in the lower thermostat housing. Remove old thermostat and put new one in. When you put the new thermostat in make sure you use a new oring, you can get away with using the old oring but you should put a new one on (their not expensive anyway). Put the top housing back on and tighten bolts. When refilling cooling system you should bleed the air out off the system aswell. To do this you remove the hose that goes to the top thermostat housing untill a steady stream of coolant comes out of it (the housing that is) then put the hose back on. Fill header tank to correct level then put cap back on. Its a pretty easy job. Hope that's helpfull