Read any of the several DVD2AVI guides on Doom9.net or videohelp.com. It does not matter which; the differences are mostly in the video part.
Basically, you rip the DVD with DVD Decrypter or Smart Ripper. Then you run the ripped VOBs through DVD2AVI and, ignoring all video options, extract the audio track(s) to WAV, downsampling to 44.1 kHz as you go. Then proceed to encode and burn as usual.