Q&A

 Master

Sounds like you got yourself a nice truck! I looked up the instructions for the heater core, and on the wrench throwin' scale, maybe a 1. I would make sure you have new clamps, coolant, good quality parts and plenty of time to get it done.
Here are the instructions:

Vehicles Without Air Conditioning:
1. Drain the cooling system to a level below the heater core.
2. Disconnect the coolant hoses at the heater core tubes.
3. From inside the passenger's compartment, remove the 7 screws that secure the heater core access cover to the plenum chamber. Remove the cover. On some models, it might be easier to first remove the glove compartment.
4. Remove the heater core.
5. Installation is the reverse of removal. Replace any damaged sealer.

CAUTION:
When draining the coolant, keep in mind that cats and dogs are attracted by 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.