Simple -- roll bar or Autoform top ( approved by SCCA as noted prior), and belts. First two items I would get for the track as the stock brakes and other items are so superior to the Gen IIs. I would like get a better oil pan third and as some have suggested maybe the best item prior to all of this would be a racing school. Having been to over 10 schools, the very best , in my estimation , is at Miller Motorsports Park. There is tons of run off, the course was actually designed for Vipers ( direct from the course designers lips ), Cindi Lux is a regular instructor and though they run Mustangs , it is a well balanced coupe with decent torque , so the school car time translates well over to the Viper.
Not a big fan of Bondurant, as though the training is top notch, the track is extremely strange and unlike any you will drive anywhere else --essentially a ribbon with wrinkles and just up and back with little, real track similarities , in my opinion.