Slide under the truck and find the radiator drain, at the bottom left corner of the radiator. (Above the inner cooler pipe. ) I use a baby pair of pliers to turn the plastic plug a 1/4 turn counter clockwise as I'm pulling out. Have a pan that will capture 3-4 gallons.
If you leave the radiator cap on, it will siphon the coolant in the overflow bottle for you. Then open the radiator cap to allow for faster draining. (we are talking about a cool radiator right?)
You can put the plug in when you've drained the radiator below the level of the thermostat... but its likely a good time to drain, replace hoses etc. unless its been done recently.
Then pull upwards on the overflow bottle, while gently prying between the bottle and the fan shroud about half way down on the bottle. Now that its outta the way, disconnect both batteries and remove the alternator bolt (10mm head), then grab a 13mm socket for the head of the lower bolt and your 15mm box combo wrech to hold the nut on the back side of the bolt.
Remove the serpentine belt if you haven't done so. Lay the alternator gently on some rags up on the heater hose/pipes. Remove the upper radiator hose, then remove the capscrews (3) that hold the thermostat housing to the engine block (10 mm socket).
Carefully note the direction of the thermostat, the gaskets etc. I usually replace the square o-ring between the housing and thermostat, then the "stepped" gasket between the lift mount and block.
Insert new parts, find some black rtv and dope your bolt threads and torque them to 18ft. after evenly snugged up.
Reinstall alternator, belt and upper radiator hose. Re-install overflow bottle and rubber hose to radiator. Insert/tighten drain and add fresh coolant (equal parts of ethlene glycol and distilled water mixture). Or purchase pre-mixed ready to use anti-freeze.
Re-ck. the coolant level after a few cycles of the thermostat opening and closing.
Have someone give you a pat on the back.
Re. ck to assure no leaks at drain petcock etc. (o-rings are available for the plug).