[motolz]

As 'Bell' said above, the problem was the seal for the output flange. I would say that changing this was a 'moderate' job. The seal was about 40 dollars. Time about 2hrs. Key tools were

1) ball head hex wrenches to remove the axle from the diff,
2) 32mm socket to remove the axle bolt (may not be necessary)
3) Air hammer to free the axle shaft after it was separated from the diff (may not have needed this)
4) Impact wrenches (just to speed things up)
5) A seal setting tool
6) New seal W0133-1934070


Unfortunately I did not take pictures so these steps may not be exact but will get you there.
1) Remove the drivers rear wheel.
2) Using the ball head hex wrenches remove the hex bolts holding the axle to the diff (#20 in suspension diagrams)
3) You will now be able to slide the axle away from the diff. It is a tight space. We found that moving it to the lower left gave the most space
4) Now you can see the assembly behind the axle this is held in place by a single allen bolt
5) Remove the allen bolt.
6) It is likely you will not be able to pull the plate because the axle is in the way.
7) Here we had to remove the 2 upper control arm bolts (#10 in control arm diagams). This allowed us to lower rear assembly without removing it.
8) Here we used the air hammer to loosen the axle from the rotor assembly but this may not have been necessary it just gave us more play to work with when trying to move the axle out of the way. The expectation is that this should not affect alignment since capser and camber are on the lowery control arms, but we will see.
9) With the axle positioned out of the way, remove the plate from the diff
10) You will see a seal in the diff, you will need to pop this out. It is held in by a tension spring around the inner seal
11) Place the new seal and using a seal tool or other, put it in place and make sure the inner spring has engaged to seat it. (it may be worth buying 2 seals incase you pop the spring on the first)
12) Once in place reverse steps from above
13) Fill diff fluid
14) Take her for a spin, park your baby, put some cardboard under her belly and check for leaks.

Really the most difficult parts were
1) Since the wheel assembly was not removed, the axel could not be removed so finding space to offset it to remove the diff plate
2) Seating the seal – Just due to being over cautious.