It's sometimes too long to go through entirely what you need to do, but there are three programs you should get.
DVD Decrypter
FlasK MPEG
VirtualDub
Use "DVD Decrypter" to extract the actual video and audio from the DVD (you can do it as seperate chapters or the whole thing in this application).
Use "FlasK MPEG" to convert the raw DVD files to standard computer video, for example, .avi
Use "VirtualDub" to save the audio seperate from the video (File > Save Wav...).
Hope this has helped you :-)