qldit

Good Morning Dmouse1, generally the pinion seal can be replaced without much difficulty by rmoving the drive shaft, undoing and removing the drive shaft flange from the diff and levering the seal out.

Carefully inspect the drive flange seal wiping area for wear and any grooving and repair as neccessary, usually carefully rotating the wiping area and flange in a piece of handheld fine wet and dry abrasive paper removes any ridging in wear areas, clean the seal seating area in the diff and fit a new seal and reassemble.

When diff seal leakage is excesive it can be caused by pinion bearings looseness, but replacing that seal does allow temporary problem fix even if this were the case.

Seal leakage can be amplified if universal joints are eccentric or worn and out of balance or the propellor shaft is not runing true.

This kind of job is not usually all that difficult, you may need to have the wheels on the ground to undo the drive flange nut on the pinion shaft, it should be pretty tight.
The flanged section normally is on the splined pinion shaft and should come off without problem once the nut is undone. Check the torque tension figure before reinstallation and ensure that nut is tightened appropriately.

Check diff oil level afterwards and you may need to top it up.
Make sure you use appropriate oil if this is required.

Cheers, qldit.