Differential Oil Change and replace with??

Might anyone give me any pointers on changing out the diff. oil on my slant? It is the only fluids I haven't looked at yet. From what I can tell it is 9 hole, so that means 7 1/4? How do I know if it is Posi? It says in the manual Posi require some other kind of lubricants??

There isn't much room to get at those top screws, backing up pretty close to the gas tank. There is no tag. In general the pumpkin looks wet with oil. I see the fill hole, if I remove it should I be able to put my pinky in there and touch oil?

Lastly, what grade oil would I need? Living in Southern California.
Also there is a brake line that seems to be connected to the cover screw.