When I did mine I didn't even bother removing the rear housing. Just remove the u-joint on the axle side, pull the driveline out (make sure you mark the orientation so you get it back in the same way to maintain balance). Use a pair of pliers and a flat blade screw driver to pull the old seal, just be careful to not hurt the aluminum. Tap the new seal in with a dead blow hammer and a small section of pvc pipe the same diameter as the metal flange on the seal. Grease the inner seal lip, put the driveline back in, hook the u-joint back up, refill it with ATF, and your done.
I would say a level 3 job is a pretty good estimate.