Hello I will answer your question,
Can you please tell me which engine you have installed in your truck?
first drain the cooling system:
Notice: When adding coolant, use DEX-COOL coolant. If silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50 000 km (30,000 mi) or 24 months. The following notice applies only to the 4.8L, 5.3L, and 6.0L engines.Notice: DO NOT use cooling system seal tabs (or similar compounds) unless otherwise instructed. The use of cooling system seal tabs (or similar compounds) may restrict coolant flow through the passages of the cooling system or the engine components. Restricted coolant flow may cause engine overheating and/or damage to the cooling system or the engine components/assembly.
then remove the serpentine belt
Then the fan clutch using a wrench large enough to fit the nut on the clutch striking it sharply with a hammer counterclockwise That is the special tool refrenced below
Then the waterpump
To put it back together, clean gasket surface, install new gasket and torque pump bolts
Tighten the water pump bolts to 50 Nm (37 ft. lbs.)
Note the fill procedure for the cooling system and use a new, quality thermostat
Let me know if you have any questions