I just did mine last week and there is a "how to" on an 04 f150 although it is basically the same as ours (you can find it by googling) but anyways here it is from memory
1. Jack the truck, support with stands under the rear axle, chock the front wheels.
2. remove the rear wheels
3. Remove the rear diff cover
4. as it is draining remove the rear rotors
5. Go back to the diff and rotate the pinion gear untill you see a small 10mm bolt on the right that holds in the pinion shaft, remove it
5. Slide out the pinion shaft and from this point on DO NOT ROTATE THE GEAR
6. You will be able to see the axles and where they enter the rear diff from each side and are held in place by "C" clips
7. Go to each side and push the axle in about 1/2" and then back to the diff and pull out each "c" clip- Keep each "C" clip with it's axle and keep track of the way it went in, you will want to replace it the same way
8. You can now remove the axle from the housing out each side carefully, try not to knick the ends of the axles (spline) set them out of the way
9. Use a small pry bar and remove the seals
10. Then use an axle bearing puller and slide it in the bearing, tighten it up and whack away until the bearing comes out, i had to use a bit of heat on mine.
11. Once the everything is all out clean it up good.
12. I put a small amout of grease on the outside of the new bearing to help it slide in and used the old bearing to tap on so you aren't hammering on the new bearing, make sure it's totally seated and you will know when it is.
13. Install the new seal, very carefully and evenly
14. drop and few drops of the gear oil into the new bearing (I'm OCD-LOL)
15. Install the axles, "C" clips, pinion shaft, and pinion bolt with a bit of loctite on the bolt
16. New RTV on the rear diff cover, set it to set up
17. Install the rotors and adjust the ebrake wheel
18. fill with diff fluid which I found a trick here from Baker- It works AWESOME, make sure the holes in the quart container are just big enough to slide the tubing in
http://www.expeditionforum.com/f73/transfer-case-fluid-change-15598/
How to replace rear axle seals and bearings in your 04+ F150 (lots of pics) - F150online Forums
Good luck and if you have any questions as you are doing it I am inboxing you my number
