That seal is about a 20 minuet job or so. All the auto parts places have em, about $6 maybe. Hardest part it the staked nut that you have to remove then torque back on, air drive works super for removing and installing it, it is a 30mm nut also.

Drain gear oil a bit
Pull 4 bolts on shaft & tie out of way.
Remove flange nut & washer.
Remove seal & wipe clean.
Install new seal, seat flush w/a socket or flat iron or seal tool.
Put some rtv on splines.
Install washer & nut & torqe to 90 ft lbs, stake nut.
Re-attach drive line.
Fill unit till it drips out of rear plug.
Done.
Clean up and put tools away.