I've been to Sebring three times now.
The track opens on the Wed before and there is plenty going on, both on and off track, to keep you amused the whole time.
I've always left (at least) the weekend before and each time have ended up in Daytona for a few days.
I'm not aware of any packages. I've always booked flights through Air Miles, using some Air Miles to reduce costs a bit). I've flown into Tampa twice and Miami once - not much to choose, except there is a fairly high surcharge on car rentals from Miami.
You can buy the race ticket on line (
www.sebringraceway.com) and collect on arrival (Will Call). (Just an aside - it would have been cheaper for me to book BA from Muncih to Miami via Heathrow than direct from Heathrow to Miami!!)
Camping at the circuit is, well, camping. We have some great friends out there who assist with some of the more difficult things. And of course an increasing numbers of CA members from the UK will be there...
For the "holiday" part of my trip I've usually just found a hotel wherever I happen to be, except this year, when we were able to catch a few days of Daytona Bike Week and booking was essential (and quite dear). I understand Bike Week is adjacent to Sebring weekend again in 2006.
I *think* my costs for 2005 were arounf the £1100 mark, for 10 days away with hire car, race tickets, the lot. Of course if you want to just go to the race and can scrounge lifts etc then the cost is really quite reasonable. The dollar was very cheap this year.