Just wanted to add some info about replacing shocks. I searched for shock replacement tips and some old posting said it was easy enough to replace the front shocks w/o removing the wheels or jacking up the truck. i did one shock that way, but the second one had a bolt that was so tight i had to remove the wheel anyway.
i have 75 k miles on my truck, and all original tires, brakes, shocks. the truck was still driving okay, but the new shocks do make a noticeable difference. and they were easy to replace. one side benefit (or maybe not) from taking off the wheel to replace the shocks is that i got to check my front brakes. they were making a little sound when i brake, but not too much. turns out, however, that the front rotors were extremely grooved, and will probably have to be replaced. anyway, the lesson is, check your brakes even if they're not making any noise.