The in-built mics in your video camera are not designed for high SPL environments. I have a similar camera and it doesn't distort, but that's probably due to the bands I tape.
If you already have external mics and a battery box, then apply your knowledge of autio taping and plug them into your video camera. The signal from your mic/battery box might be too high for your video camera so you could use a -20db attenuation cable as well.
If you don't have a mic iinput in your camera then you're out of luck.
You could also audio tape the show on a DAT/hard drive/miniDisc recorder and sync in to your video in post.