I have been searching the archive for the procedure. Here are the conclusions and questions I got:

1. I guess I found the drain plug. It's a plug that can be turned with 14mm allen wrench.
2. Where is the refill plug? What size and type of wrench should I use?
3. It is advised to clean the vent on top of the differential. Does it hold true for my car?
4. Should I lift up the car to gain access under it? If yes, driver side or passenger side is prefered?
5. Any other tips am I missing?

Thanks.

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Harry (94 C280)