RE: My new ride, heat doesn't work!
Its not too difficult. It's best to reverse flush the systems.
I believe the hoses for the heater core are located in the same spot on your truck. To the right (passenger side) of the master cylinder. Theres two hoses. Disconnect both of them, connect a water hose to one of them and put the other in a bucket (or, at least aim it into a bucket). Run hose water thru the line until the water comes out clean.
Water flow thru the engine block is from bottom to top, so to reverse flush you would go from top to bottom.
Water flow thru the radiator is from top to bottom, its probably safe to just flush it in that same direction.
The key is to get clean water out of each item.
Of course, coolant/water concentration is 50/50. If you buy the pre-diluted stuff don't add water (but its more expensive that way). If you don't buy the pre-diluted stuff, its a good idea to use distilled water, since the minerals are removed.