See Figures 1 and 2
Fig. Fig. 1: Thermostat servicing - 5.0L (VIN E) and 5.7L engines
Fig. Fig. 2: Removing the thermostat from the intake manifold
REMOVAL AND INSTALLATION
Drain the cooling system to below the thermostat level.
When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.
Disconnect the upper radiator hose from the thermostat housing. Loosen the clamp on the coolant by-pass hose, on the 5.0L (VIN Y) engine only.
Remove the two retaining bolts or studs from the thermostat housing and remove the thermostat.
Use a new gasket when replacing the thermostat.
Fill and bleed the cooling system.