1) Yes empty cabs are there, I usually don't stick around to see what they sell for.
2) $4 for parking out at the fairgrounds, free to get in.
3) Bring an extention cord, some cabs are close enough to outlets to plug in, but there are some that you will need an extention cord for. They also plug each game in as they are auctioning to show working/non working state.
4) There are usually a couple mame cabinets, usually pretty poor quality compared to what people on this board build.
5) Sorry don't currently have an extra cab, but I will probably be at the auction.
Other things to note, you should bring cash so you don't have to pay 5% premium. Don't come too early, the US amusement auction in September took forever to get to the cabinets, ~10:00 start, sell crap 2 hours (odds and ends), sell megatouch games for ~30 min, sell coctails fro ~ 10 minutes, sell gambling machines for ~45 minutes, then start on first row of games (19"), then pinballs, then race games, then 25" and bigger, then empties. Plan on being there ALL day if you are looking at the empties. I had to leave at 4:00 PM last time to go to a baseball game and they had just gotten through the 19" cabinets. See you there if you are going.