You have complete control over priorities on a ReplayTV via the conflict manager. If it conflicts, on that screen you set how to handle it. If the conflicting show that would normally record is not on, the other show will record fine.

If you need to change this, you do not need to delete all the shows set to record and start over. Simply change one and it pops the conflict manager back up. Or pop up the channel guide, find one of the shows set to record (noted with a red dot for single record or two for multiple record) and hit the record button. This also causes the conflict manager to reappear.

Edit- Part of the problem I think Tivo users seem to have understanding a ReplayTV unit comes from all the terms Tivo assigns to things. "Season Passes" is a great example. TiVo owners seem to expect other devices to also call recording a show multiple times a season pass.