It's really pretty easy, almost as easy as ripping a CD. I'd check doom9.org for a tutorial, and just follow the directions they give for ripping a DVD, but stop when you get done with the audio. There should be a way to rip it into chapters, too, otherwise you'll be left with one really long track.
PM me if you need some help doing it. It'll give me an excuse to rip some of my own DVDs. =]