what spike said, its easy to get bogged down obsessing over the details and piddly stuff and a land rover is a bad vehicle to be that way about.
In your case I would change your oil, two bottles mixed with t6 should make for some very thin viscosity.

 

And whatever swollen rubber parts fix has taken place is done, after a couple of days or two - three hours or driving.

 

The rear main might have been an oil pan leak after all. There are a couple od screws deeply burried in the back part of the oil pump next to the bell housing, where some oil was seeping. I just wanted to make sure they were tight and the leaking one was so loose that I could turn it without much force and needed at least 2 turns. And this was not the only loose screw. Most of the rear screws were some what loose and I tightened all of them. Oil filter housing is coming Monday, will drain oil when I install the new filter housing.

 

Oil filter housing is easy fix so will fix that one and not worry about the rest, unless there is a problem