The easiest way is to see if there's a recording program bundled with your sound card that allows you to record whatever sound your computer is putting out. I then put the DVD in my DVD-ROM, play it, hit record, and it creates a .wav file from the sound (I've done this with all sorts of stuff, including Stevie Ray Vaughn live at Montreux). I then convert the .wav into mp3 and voila. As long as you remember to stop at the right spots, it shouldn't be too hard.
