Just a recommendation on the helmets... Look for a helmet that is Snell approved. The majority of motorcycle helmets are DoT approved, but not Snell approved. This is because the Snell helmets go through a much more rigorous testing procedure. Additionally, Snell approval is required in SCCA racing, so if you are looking at running outside the Arizona club you might want to take that into consideration as well.
Personally, I am partial to full-face helmets. Now, I do come from a motorcycling background, so perhaps this comes into play, and I am real big on safety. Bear in mind that you are travelling at 100+ mph... with other people on track with you, should something go awry, I would want all the protection I could get. Comfort should be a factor, yes, but you can get comfortable full-face helmets, too. They do make open-face Snell-approved helmets, so if you want to go that route (and many people do) it is open to you.
Best of luck, and have a blast out there.
