I want to replace the u-joints on the rear driveshaft of my 99 4wd. I've replaced the u-joints on a 79 and was wondering is there a special way or trick to doing these on my current truck.

 

Hi. I'd say the principal is the same. If you've got a double joint in one housing with a yoke inbetween them that's called a cv joint. The principal is the same on those but it's like a jigsaw puzzle. You should get a parts breakdown picture of the cv joint showing where everything goes. I think there's a spring in the yoke somewhere.
If your shaft has a slip joint with splines in it, first remember where it is in the assembly and get the timing right if you take it apart.
Dave.