Final drive unit oil seal & bearing queries

Deffender 110, front Rover Final Drive/diff

Would I be correct in saying the final drive oil seal number is FRC8220? Can this be changed in situ with oil in the final drive unit or would I have to drain?
In addition, can the outer pinion bearing (sits behind the same said seal) be replaced with the final drive on the vehicle?
And finally, the castle nut for the flange is to be torqued to a specific value correct?
Thanks in advance for your consideration.

theres a choice of 2 seals depends on what mudshield is fitted to the flange

one on the left needs frc8220 oil seal, one on the right needs ftc5258, its possible but difficult to change front bearing if you need to do that stripping diff is a far better idea, 95 lbs ft but just quite tight will do, the torque is just to stop nut coming loose

Thanks a bunch. The flange on the right in your pic was the type I had previously. With my "new" diff I just got from a disco 1 the flange on the left is what I currently have. I believe I tightened the castle nut too tight during installation so I shall get back to it very soon to rectify.