You can go merely as a spectator, but there is a registration fee for participants and I think you can't get into some events without your participant badge. The first main events occur at Road Atlanta. Petit LeMans precedes Ofest and then the club race is Sunday. Other than registgration and a Sunday night reception I don't think there's anything in Greenville this weekend. Monday is the first driver school and autocross day and those events continue again on Tuesday so cars and drivers can do both events. There are receptions, dinners, viewing of the photo contest and model contest, vendor booths, plant tours, etc all week. The full schedule is at Oktoberfest2000.org.