I've been here 15 years and hadn't had a power outage yet.
I wouldn't buy a generator, but if you have one, bring it just in case.

One is never guaranteed a single tee time even if the night before you put yourself into an empty slot on the tee time system. It depends on how busy the course is, which depends on the course, time of day and time of year, among other things.
But if you see a bunch of empty slots on the night before, your chances are good.
Finally, you can ask at the desk on the day you play if you have been put with other golfers.

It can be NG or Propane with the flip of a switch, mine is set for NG as we have NG in the home. The price was approx $11,000, including the site plan and all the permits, including our very own ARC and the Sumter County permit. I have pictures on my cell phone, but posting them here is beyond my pay grade, sorry.