Upload & Sell: On
Buy a 50mm f/1.8d lens for about $100
Auto ISO set to top upper level of ISO1600
or manual ISO to ISO 3,200 H1.0
Aperture mode set at lowest aperture.
A monopod (don't stand in front of anyone, adjust to you sitting in your seat)
steady the camera on a seat back if no monopod
Make sure vr is on
Maybe use 2 second shutter delay to further minimize shake (if camera is on seatback or monopod
Take some practice shots a few days before the play to see what acceptable shots will look like and at what ISO (grainy is better than blurry)
Be sure and have the shutter release "beep" turned off!
By the way, that's a slow but good combination (D80 and 18-200mm) I had it long ago. But it's not a great indoor, low light combo. It's a generalist kit...