This will be my first time at Oshkosh. I was planning on camping under the wing, but an acquaintance told me that several years ago he had found that all the available spots were taken on or before the first day. I plan to arrive some time Sunday, so I'm concerned there won't be anywhere to camp when I arrive after my 3+ day flight. So my questions are:

-- Is it likely or even possible there won't be any spots available when I arrive?
-- If there are no spots available, what happens? Will ATC wave me away to land at some other airport? If that happens, would I be able to camp at the alternate airport? Or do I fly into Oshkosh, park, leave every evening, find a place to stay, and fly back the next day?
-- Is it wise to pay the camping fees on line before I go?

I really appreciate any advice you can give. Thanks!