Need location of thermostat in a 1998 taurus with a 3.0L 4V, 24 Valve v6

The thermostat is located inside the water neck on the drivers side of the engine. You will see a large hose going to the top of the radiator and to the water neck.
You will need both the thermostat and gasket before you start, I would also recomment some RTV sealant, and two new hose clamps and about a half gallon of coolant mixture. Start by draining about one gallon of coolant from the radiator, via the valve located on the drivers side bottom of the radiator in to a bucket. Next remove the large Hose from the water neck and radiator. Next remove the two or three bolts that hold down the water neck, and gently pry it loose from the intake manifold. The thermostat may come out with it or may stay in the manifold. Remove the thermostat. Clean both the intake and water neck well, removing any old gasket material, oxidation or sealant. Next install the thermostat, some lock into the water neck by a quarter turn method, some you will find handy to RTV in with a small amount spread evenly around the edge between the thermostat and water neck recess for the thermostat. Be certain to orient the thermostat the correct way, the valve end goes away from the engine, and the small tower that retains the spring goes towards the engine. Install the new gasket with a small amount of RTV to hold it onto the water neck, then a small amount to seal between the gasket and manifold. Install the water neck with the original bolts, and tighten snugly, but don't over torgue them. Next replace the hose clamps and if the hose is in good shape, re-install it. If the hose is not in good shape replace it as well. Next put the coolant you drained in step one back into the radiator through it's fill neck. Use the spare coolant mixture to top off the system. With the Radiator cap removed, have an assistant start the engine, and run with the heater set to maximum heat, until the car is at normal opperating temperature. Have your assistant rev the engine and hold it at about 3000 RPM. This will cause the water pump to pull the maximum flow of coolant into the engine to purge any air bubbles that remain. Tap up the coolant and replace the cap. Fill the overflow bottle almost to the top of the bottle, this will allow the engine to pull any necessary coolant into the system as the engine cools down over the next couple of days. Keep an eye open for leaks and watch the temperature gauge over the next few days, any rapid spikes and drops in temperature while driving, indicate an air bubble. These cars are well known for air bubbles, and if you have one, you will have to go through the purge steps again until things normalize out, elsewise you could warp a head or crack a head.