If there is pitting on the ball then its really time for a new one. You can bugger about and smooth/fill the pitting, but you're just eeking out life from the old one.
Having thought about it, it is unlikely to be oil in the wheel bearings, and therefore coming out from the hub seal. Can you see any oil traces coming down from the centre of the brake disk (axle side).
You can change the oil in the swivel for 'one shot' grease. Put in by Land Rover as its thicker and therefore less likely to leak. Personally I think its a silly idea, I want to know when its leaking as leaking means water etc can get in.