The thermostat is in a black plastic cube on the driver end of the engine, with rubber hoses attached to various sides, held on by three bolts. You may have to disconnect other crap, such as the PCV pipe, to get it loose. It's a pain. The thermostat is between this cube and the engine block. There's a thin little o-ring thingy that goes around it... a thin touch of RTV silicone on that ring can be of value when reassembling.
