If you are facing the mountain, the seats are on the right side of the theater - about 1/4 of the theater (the far right section) is reserved. How early you get there determines your choice of how close or far away you sit. We always got there about 30 minutes before showtime - but I think that depends more on how crowded it is when you go. I didn't think the seats were bad at all.
You enter through a special side entrance, near the entrance to Hollywood Studios. Everyone else enters near the Tower of Terror. However, everyone exits through your special entrance area.
The only problem we had was our ADR time, I made it 3 months out for October and we had to eat at like 4:15-4:30 or so. Not my ideal time, but we were fine with it.