Also, it might be a good i

Also, it might be a good idea to manually white balance your camera. When they "blackout" all the lights, it throws (at least the GL2’s) auto white balance off.

as tonsofpcs said, it would be a very good idea to attend a dress rehearsal, so you can be more prepared.

Now for audio, I’m not the most experienced, but here’s my two cents.
There must be a audio mixer working on the set. He/She would probably be there at the dress rehearsal (and other rehearsals), and you want to talk to them about how its going to be done.
From my perspective, there’s at least two ways:

1. You can record the audio from the mixer separately and sync it to your video in post.
2. Find a long XLR cable and connect it from the audio mixer to your camera. (You might need an XLR to 1/8th inch adapter)

You’ll also want to record the audience as well, which you can do from your camcorder. Use an external mike.
Remember (even though this is somewhat obvious) – Don’t stop recording!

Goodluck, I hope this helps