The slip yoke is on the end that mates to the transmission, you cant see it until you pull the driveshaft off. When you remove the bolts, tap that same flange with a hammer (to knock it off the rearend), and the swing the driveshaft down and away from the rear axel, and then pull the drive shaft towards the rear of the truck and the driveshaft and slip yoke will slide right out of the transmission end.

You need to be very careful not to drop the slip yoke once it exits the tranny as it could damage it.

Once out, you can re-grease the slip yoke and examine the ujoints....IMO, if you have the means and tools to change the u-joints, I would do it wether the joints are good or bad, for the simple fact that you have the drive shaft off, and the u-joints are relatively cheap.