Do a google image search for "Volvo Haldex".
There's a few pictures of in situ Haldex units, so if that's what your's looks like then it's a Haldex you have, if not it's a viscous
Googling "Volvo viscous" didn't bring up any pictures of the viscous coupling in situ but a few diagrams so you should get a good idea what you're looking at.
If the oil leak isn't significant, as in dripping, then I wouldn't worry too much....
The angle gear is at the other end of the prop shaft, it's the bit at the back of the gearbox where the prop fits.