I think you've misunderstood the question. He needs to deliver discreet 5.1 tracks as wave files not a DVD or .vob file
In Vegas set up your 5.1 mix as required and render a multichannel 48KHz wave file.
Dealing with a stereo mix means the you'll really have an LoRo (not LtRt) mix that won't decode into surround. You can cheat this by using the surround panning but the problem is that putting too much of the stereo mix into the surrounds will just make the mix a little indistinct.
You could try a very short delay on the surround channels. Ideally though you're are better off creating the 5.1 mix from scratch not from a stereo final mix.
Whatever the 5.1 mix you create you can then re-import the resultant multichannel file into a new Vegas project and, without adding any additional processing output each of the stem tracks as a separate mono wave file in 48KHz sampling rate.
Clearly identify the individual files as per the PDF you referenced. Note that Vegas doesn't always conform to the track layout for multichannel 5.1 files that the PDF requested so make sure you monitor each mono file, correctly identify and label it accordingly Left, Right, Centre, LFE, Left Surround, Right Surround.
Don't forget your reference tone @ -20dBFS.
Also countdown pips for sync reference on each mono file as Vegas isn't going to supply you with any timecode metadata in the wav file.
The encoding for cinema will then be handled by NCM.
This is all a pretty normal way of handling 5.1 for cinema.