Well I should be getting it in the mail in a couple week, so I’d best ask in advance.
When/where in the game is the disc change?
at the end of day 5, which is practically the end of the game.
How much is on disc 2?
1 or 2 dungeons, plus a series of final battles. You can leave the dungeons at any time until you complete the second dungeon (Museum). After that, you’re stuck.