Are you replacing the driveshaft ujoints or axle ujoints? If axle ujoints, as said above, it will take a little longer than a couple hours, plan a day to be safe. If your doing the driveshaft ujoints then you can do them in less than a couple hours. I use a socket that's just a hair smaller than the ujoint cap, placing the driveshaft on a block of wood and hitting the socket to drive the opposite ujoint cap out, it will take a few hard hits with a BIG hammer to get it started.