[Chip]

I have a D90. I've used a borrowed 70-300VR in church (with windows) on a very bright, sunny morning, as was surprised at how incredibly slow that lens is for inside shots. Even turning up the ISO to 3200, I had a hard time getting a useable shutter speed. Camera shake was an issue.

So, I'd recommend using the fastest lens you can either find, rent or borrow, and also turning the ISO up (to 1600 or 3200 if needed). Borrowing or renting an SB600/800/900 flash could also be helpful; mounting the flash on the camera in TTL mode and bouncing it off a white ceiling or wall is pretty simple and helps quite a bit.

I'd also recommend shooting in aperture mode and using the widest aperture possible, since the preset indoor mode might make the on-board flash pop up.

Any way you can go to this place before the party and take some test shots? Expirmenting before the party might both make for better shots that count and make it easier on you during the actual party.