I have an upcoming flight on FL ATL-LGA. I don't fly FL often and am wondering how the buy-up program works. I searched a little bit and I assume, if available, I'll have the option when I check in online for my flight? If I buy up, will I receive all the benefits of a normal business class passenger (2 free checked bags, elite security line? any Airtran credit bonus for flying in the front?)

Thanks for any help. Flight is on a Friday morning, monday morning return, if it matters.