Most solid axles (like my D35's) have tupes open to the differential lube oil. The oil is allowed to mingle with the bearing grease (both actually lubricate the bearings, but the oil helps to carry heat away from the bearings as well,) and the seal is at the outboard end of the axle shaft.
Since the bearings are pressed onto the shaft, you'll need to remove them to replace the axle seal - so you might as well replace those as well (they're typically cut with a grinding wheel until they pop from internal stresses - it's a healthy press fit!) I usually cut my own off before I take the shafts in to have bearings pressed on - it cuts the bill by half, and you don't need to go all the way through! Get about 2/3 through the inner race, and you hear a loud "POP!" as the metal lets go. Notch to remove.
Make sure the seal and shaft are greased before you install the seal - a seal that starts running on a dry shaft will fail quickly.
As far as gear break-in, I can't give you anything off the top of my head, but if you check Randy's Ring & Pinion (
www.ring-pinion.com or
www.ringpinion.com, I think) you can find instructions on both installation and break-in there. Since the process of breaking in a gearset is essentially runinng the gears together until they take a set to each other, it's really important that it be done correctly. Gears are not usually lapped at the factory, and they'd still need to be matched anyhow.
The only XJ axle I can think off offhand with inboard seals (the oil seals are at the differential, rather than at the wheels) is the front-end Dana 30. Everything else (c-clip or no, light or heavy duty) seals at the wheel end.
5-90