Hey Coach
As you may have guessed, this isn't a simple process, but it is doable, via a few steps, and it may require some additional software.
Since it is likely an unprotected DVD -- ie produced by your client using iDVD -- the process is a little easier.
I have used Extractor in the past, not the most beautiful user interface on OS X, but it does the job well:
http://denisx.dyndns.org/extractor/
Basically what you need to do is convert, or demux the .vob files into separate MPEG2 (a.k.a. .m2v) and audio streams.
You should then be able to import these as you normally would into DVD SP 3.
Good luck, and I hope this helps.
Regards
Peter
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raycity* media