You do need to kind of finesse it in there. You won't harm anything if you don't force it. Hard to describe how to do it. If i am describing it correctly, I think the way I do it is to put it in at a slight angle, so I can start one of the screws, then twist it so I can start the other screw. It'll feel like it's sitting flat against the back of the alternator. The important thing is to get it off so you can look at the brushes. The tip on one of them will ptobably look kind of dull, like it hasn't been contacting the ring.
You don't need to disconnect the battery even.