I don't think you have to do anything to the front to make your truck a dually. They sell dually conversion kits. I have seen them at places like Chrome Wheels (Houston,
www.chromewheels.com). I am certain others carry them. You need to decide if you want a dually look, or dually function. You can go cheap and not change much in the back except getting fenders and some adapters for the dual wheels, or you can beef up the back to hold the weight a dually is built for.
You might also want to consider some kind of heavy duty bumper for those a$$holes that keep hitting you!
RL