I love Sun N Fun. Used to go every year when I lived in Orlando. My wife and I used to drive down for a whole day, until I decided to fly in. That spoils you, and you'll never wanna drive again. I've never been to Oshkosh, but from what I've heard Sun N Fun is a mini-Oshkosh.
There's a LOT of vendors down there, so there's plenty to gawk at. The airshows are hit and miss. It's best to check out the performers before you pick a day to go since they're different day to day. I got lucky and managed to see a show with Patty Wagstaff and Michael Goulian. It was the only day that week both performers were there.
If you're gonna fly in, get the NOTAMS and know 'em. It can be sorta confusing the first time, and it's weird not reading back instructions over the radio. What they'll normally do is set up a lake as a "holding pattern." When you arrive, ATC (actually guys on the ground with hand helds) will be telling you to "find someone, get behind them and get in line." They'll call out planes by type and color "white high wing Cessna" for example, then clear you to fly over a landmark. They'll be strobes to follow to get you onto the downwind, then ATC at the airport will tell you which spot to land on. The taxiway (since the runway now has airplanes parked on it) has three spots painted on it. Land on the spot they tell you.
Getting out is a lot easier. It just takes forever. Make sure you buy tie-downs BEFORE you go. Made that mistake and had to pay for the seriously overpriced tie-downs there.