The clips, cuts, edits, etc are gone. All you've got is what you see when you put the DVD into a DVD player.
Rip with MacTheRipper to preserve quality and the menus/chapters. Unless you use something more capable than iMovie, you'll have to convert and reduce the quality at least twice (once to get in, once to get out) to get back to a file for distribution. MPEG Streamclip comes to mind.