Hey stsguy5, welcome to the forum!
Hard to say when they will get back -- they are notoriously busy and distracted, and the Email-pipeline is always overflowing.
The price is for the length of the event. I don't think there's a reduced camping cost for part of the event. Keep in mind, it's only for the site. Pilot/Spectator registration is in addition to this.
If you register a spot, one will be available for you when you arrive, but they are assigned on arrival. You can always ask to get a block off to the side when the first guy arrives, and you can schedule to arrive somewhat simultaneously, but there isn't another way to guarantee you'll be camping next to people you know when you arrive. I can say you'll be surrounded by other great people and will probably know your neighbors when you leave
As for planes, the flightline is Electric only . . . although in past the occasional rubber band, candle, or rocket powered airframe have snuck in an appearance . . . but IC engines are ground-based at this event.