Elvis, Sportsman class is an entry-level class for practically any kind of racebike. It's intended for Novice racers that need to get up to speed in a more relaxed group.
Even though you have racing experience, you should take the New Racer School that is coming up in April. It's a good opportunity to meet the people that run the MRA and all the instructors are Expert-level racers. Bring any documentation you might have of previous racing experience, and they can tell you if you need to start off as a Novice or Expert racer. Then you'll know what classes you need to prep your bike for...