The 3.4 liter engine thermostat is located on the drivers side of the engine, where the radiator hose goes in. This thermostat can be hard to remove, the water outlet has two bolts, the upper is not too hard to get off, the lower one is in a very tight space. The GM proceedure calls for removing the exhaust crossover pipe, however you can remove it with removing the pipe. The problem is getting to the lower bolt. If you can get a short wrench in there, it can be done. The water outlet is sloted where the lower bolt is, so you do not have to get the bolt all the way out to remove the water outlet, just get it out about 3/4 of the way. I will give you the GM instructions.