How to replace the thermostat?

Next to the belt pulleys you'll find a housing with a radiator hose clamped to it. Disconnect the hose and remove the bolts holding the housing to the engine. Make sure you drain the coolant first to avoid making a mess. The thermostat should come out with the housing. Make sure the gasket/O-ring is completely removed with it. Clean the surfaces to make sure they go back together nicely. Reverse the process to reinstall, making sure to properly place o-ring or gasket, purge all the air from cooling system by removing the radiator cap, starting the car and turning the heat all the way up to it's highest and hottest setting. Use the defogger so it comes out the vents under the windshield. Watch the radiator fill for bubbles while checking for heat and watching the temp gauge. This process can take up to 30 mins so be patient. Once you're getting hot heat and the bubbles are done, refill coolant and put the radiator cap back on and you should be good to go.