I've never replaced a rear axle bearing, but packed mine many times. If you pack it with grease, it may work well enough to drive it some more.

My Nissan book says

1. remove the drum, then remove the four bolts holding in the axle
2. pull the axle out (easy enough, I put the drums loosely on backwards and "hammered" them off pulling sharply on the drum, sometimes a length of chain can be used if they are hard to get out). If you have a slide hammer, that migh work as well.
3. replace bearing locking collar by "nicking it deeply with a cold chisel in several places. It will then slide easily [off the axle]. Be careful not to damage the axle shaft with the chisel.
4. Set the bearing remover ([Nissan Tool] ST37130000) and remove the wheel bearing." ST37130000 looks like a very long tube with a threaded crank. I'm guessing it's a very long version of gear puller.

By the way, the bearings really do need packing every year when they get worn down (unless you put new bearings in). Using the thick "axle grease" rather than the "high-temp disc brake grease" will help the 90-wt from leaking past the seals so fast. New seals will help, but ball bearings always eventually wear and cause some play in the shaft, hence a little leaking past the seal. Roller bearings as used in disc brakes is a far stronger longer-lasting design. I guess the advantage of ball bearings is less expensive and less friction.