unbolt the 4 bolts on the back of the wheel assembly. You may or may not have to remove the brakelines as well. Leave the tire and wheel mounted, and jack the truck up so there is just a little bit of space between the tire and the ground. With a little pulling, the axle shaft should slide right out.
Leaving the tire and wheel on does a few things for you.
1) gives you something to get a better grip on when pulling, you might have to put some effort into it.
2) in case the truck shifts and/or falls off the jackstands, the tire will keep the truck from falling very far
3) now you don't leave the axle hanging halfway out of the axle tube, resting, and possbly damaging your axle seals. The tire will hold the axle shaft centered (for the most part) in the seal. I'd go ahead and replace them anyway, while you've got it apart, but a lot of people don't.
Haha, you give a little more detail than I do.
