Unless you're wanting to get fancy with the video, you could use windows movie maker to sync up the audio with the video.
If you have another pc other than the show computer, easiest way to get the complete show audio might be to cable from the headphone jack on an FM receiver to the aux input on the pc and record the show's audio broadcast. Once you have the video and audio captures in movie maker its pretty easy to bump the audio into sync with the video.
Good Luck.
Greg