you can do it all with just the mplayer package. First create an avi file containing an empty video stream and mp3 audio
mencoder dvd://1 -ovc null -oac mp3lame -lameopts cbr:br=192 -o michael_flattley_is_really_annoying.avi
and then remove the audio to a seperate file
mplayer -dumpaudio michael_flattley_is_really_annoying.avi -dumpfile him_an_his_silly_feet.mp3
but then why you'd want to convert it to mp3 in the middle. if space is not an option then just straight to pcm...
mplayer dvd://1 -dumpfile he_thinks_hes_so_cool.wav -ao pcm
i think that's the right syntax for that...