Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
It should take you about an hour. You will want to make sure that you get all of the old gaskets of before installing the new one. Here are the steps for it, thanks
REMOVAL WARNING: DO NOT LOOSEN RADIATOR DRAINCOCK WITH SYSTEM HOT AND PRESSURIZED. SERIOUS BURNS FROM COOLANT CAN OCCUR. Do not waste reusable coolant. If solution is clean, drain coolant into a clean container for reuse.If thermostat is being replaced, be sure that replacement is specified thermostat for vehicle model and engine type.Factory installed thermostat housings on 3.9L/ 5.2L/5.9L engines are installed on a gasket with an anti-stick coating. This will aid in gasket removal and clean-up.
CAUTION: When installing the serpentine accessory drive belt, the belt must be routed correctly. If not, engine may overheat due to water pump rotating in wrong direction. For correct 3.9/5.2L engine belt routing. The correct belt with correct length must be used.
Your welcome and come again whenever you need, thanks