"you need to export separate video and audio streams of a project that can be imported into DVD Studio pro"
This is called "Elementary Streams" and is used by many other editors. Although your dvd producer can simply tell his dvd authoring module to use the audio in the video file by loading the video file into his audio section separately.
In VS "Share -> Create sound file" [Save As Type]=wav, click on the options and make sure to use pcm with 48khz 16bit stereo and save your sound file
With the Same Name as the video file which you will do next.
Example: xyz.wav
The next step is "Share -> Create Video File -> Custom" [Save As Type]=mpg.
Then Options "General track make this
Video Only, make all the other necessary settings to export a dvd compliant mpeg2 file. Then make sure to assign the same name to the video as the sound file. His dvd authoring module will look for the same name sound file when he loads the video file. If VS assigns the extension of mpg to the file then change it to MPV (mpv).
Example: xyz.m2v
Video Only = xyz.mpv
Sound file = xyz.wav
I know, doesn't sound simple, but you asked. Also the person making the dvd should be able to use a straight mpeg video file. If he knows what he's doing he could split the video & audio for you either way to get it to work in his program. But in most of those programs you simply load the standard mpeg file twice, once for the video & once for the audio section.
And I am sure he will charge you a lot more too... 