To fix the axle seal involves pulling the entire carrier out - not exactly hard, but parts need to be put back at proper torque and in the same place they came from (bearing caps etc.)
That axle-shaft Ujoint looks old and crusty. If you're pulling the diff apart to fix a leaky seal, you should take the time to also toss in a new set of ujoints on both sides.
'00 XJ Sport, White - almost done for now...
'11 Town and Country - people mover :-(
'88 XJ Up Country, '01 XJ Sport, '08 KK Limited, '98 XJ Parts Donor, '07 XK Limited (the Stall-ander)