If it's the shaft (drums are clean) pop off the hubcaps, remove the split pin, undo the shaft nut, remove the washer, prise out the felt washer and replace.
...but I bet it's the hub bearings, remove the 6 drive member bolts and prise out the half shaft with drive member attached. Using a punch, hammer back the lock washer, remove the lock nut and washer. Undo the hub nut, remove nut, washer and the complete hub. Prise out the seal from the back of the hub, repack the bearings with LM grease, press in a new one and reassemble.
You'll need
hub spanner (only a few quid, worth its weight in gold)
2x hub seals
2x drive member gaskets
Have a good feel of the bearings before you start, if the hubs are out it's relatively simple to replace the bearings at the same time.