Yes it can go in the glove box. If you get the Alpine unit made specifically for the Volvo, it should come with a custom bracket that takes up the entire glove box. It is only a braket/mount, not a new interior.

If you don't get the Alpine unit made specifically for Volvo (if it is the Volvo unit, it says Volvo on it instead of Alpine), the brackets that come with the Alpine unit can be used.

Depending on the model, it may be plug and play. It all depends on which Volvo deck, and which changer (alpine or Volvo). The most important part is to make sure you have the Alpine deck. At that point, the worst that can happen is that you'll have to go out and buy the adapter.