I tried exporting my video to DVD, unfortunately the only audio options seem to be set to 48MHZ for audio. This has caused me significant problems in the past, because most of my sounds/music is at 44.1 MHZ and when upsampled, it gets distorted.
The only export setting I see with an option to change the audio sample rate is
"High quality, VBR transcoding of Progressive-frame content (max bit rate = 7)"
BUT, the drop down thing to change the MHZ is unclickable.