Grab DVD decrypter to ripp the DVD vobs.
Use DVD2AVI as a file server.
Use Headac3he to demux the audio into a suitable format.

Here's a method for copying DVD to a KVCD/KDVD format. All you need to do is strip the audio. I've never only used the Audio but the audio using this method has always been very good for movies/concerts I've backed up and should work great for your application. Much of it depends on the settings choosen in Headac3he which is explained in the method. Although, it may take a bit of experimenting...

Let us know how is goes, Jag