how many u-joints does my truck have.some say 2 and some say 3 and some say you have to ghange the whole drive shaft.

Depends. Some have a single piece drive shaft with 2 u-joints. Some have a two-piece drive shaft with a center bearing and 3 u-joints. Which do you have?

Be sure to check all u-joints also to make sure none are locked up!.. Move each joint in all directions, should move freely!

Mine has three, just replaced the center bearing and one of the u-joint.It was a bit of a job, but I got it done.