This question has been answered in these forums numerous times. Handbrake will take a DVD to a QuickTime or iPod file in one step. MacTheRipper will strip a DVD.Then you back up the ripped movie to DVD with DVD2one.
If you have a VIDEO_TS folder on your hard disk, you can play it in DVD Player by choosing "Open DVD Media" from the File menu and directing it to the VIDEO_TS folder. You can also play it with VLC or MPlayer.