The U-joint casting will have a grease nipple if it is meant to be serviced. Check each joint in the drive and half shafts and you should see a small grease nipple from the + piece between the shaft yokes. Clean it off and use a common grease gun to apply grease, rotating the shaft to get the best clearance on the nipple. I'm sure we could get into a rauchous converstation about what kind of grease to use, but any common suspension grease will do. Once filled, the grease will start coming out of the four ends of the u-joint. Wipe it all down nice and clean or the grease will spin off and on to your car. If you don't find a grease fitting, it could be missing; look for a hole, the u-joint was not meant to be serviced. I have used both types and can't report any longevity difference. I seem to go through half shafts so often, I bought a spare set of shafts. You will notice the joints going bad by clicking from the axle shafts when you start out in first gear. Very, very slowly let out the clutch with no throttle until the car just begins to roll. You will hear perhaps a series of clicks as each u-joint reacts to the torque. Loud, noticable clicks are bad and mean the joint needs to be replaced.