you simply remove the lower radiator hose . then you can flush it. i remove the heater hose and attach the garden hose right to the hose barb sticking out of the manifold where you just removed the heater hose from.
Don't remove lower radiator hose, there is a plastic valve located by the passenger front wheel. Where exactly I don't remember, but put a 5 gallon bucket under it, and you'll be fine. Leave the truck off. When it is all drained, close the valve and fill the entire reservoir with water and run for 15 minutes. Drain this water in to the bucket, and proceed to close the valve and put in your 50/50 mix of water and coolant. Make sure you don't let the family pet get a hold of that coolant bucket, its pretty toxic stuff.