Im not going to go into detail on how to lift the SS and make it safe to get under... That all goes without saying...
When you look under the rear of the SS you will see the final drive..It will have 2 plugs that can be removed with an allen wrench..
One is the drain on the bottom side and the other is the fill hole.
The drain plug has a magnet on it. Inspect it for large metal parts. Hopefully it will just be a slightly sludgy metal coating on the magnet.
Clean it off and once its drained put it back in a tighten it to 10 - 14 lb ft. That is (foot pounds)
The fill hole is also the FULL level of the final drive.. You will fill it till it runs back out that same hole....
It takes .78 QT of fluid technically. Just make sure its full to the bottom of the fill hole.. If you can rotate the drive shaft and you can see that its full.
Watch the video, it will show you how to absolutely tell if your full.
Here are the picture of the items mentioned above...