Is this pump leaking sea water from the little hole between the pump and the
engine? If it is then you need to get it fixed before the baring fails.
Defender has the best prices for "major" rebuild kits. I have used Depco
(impellor, seal, gasket = $90) rather than rebuild my own but I understand
it is not that difficult. Depco pulls the seal and inspects the baring.
If this pump is leaking oil then it is a matter of your personal tollerance.
Now if the 4-108 rear seal was this easy I could stop buying diapers.
-Allen