first, do a search in the audio/video forum, this has been covered many times. you'll need a demuxing app like bbDemux to separate the VOB into audio and video.
second, if you have DVDSP and FCP, why don't you use them? forget iDVD. as Angus_D said, that's strictly for making your own DVD's, not copying stuff, or editing mpeg2 files. even if you could get the demuxed VOB into iDVD, to make the disc, iDVD will re-encode everything into mpeg 2 REGARDLESS if it was already mpeg 2.
tr