Hi Doug,
You will be fine. Helmets will be made available if needed. I believe there was a box to check on the Track Day Reg form including size. Make sure you let us know if not on the reg form.
Clothing should basically be shoes you are very comfortable driving the car with. I would always recommend a pair of driving shoes especially on the track. I like the Simpson shoe because they are thin soul'd and tight around the foot without a bunch of extra width. A driving shoe will give you a better feel of the pedals and foot box, and you know where the edges of your feet are. A good set of driving gloves also helps with car control and safety. Apparel can be jeans, no shorts, and a long sleeve shirt is recommended. I also like to recommend a neck brace although not required. They help to limit head movement. Once you wear one, you’ll feel naked without it.
Everything will be explained it the Packet but let us know if you have any questions. Oh yeah, prepare to have fun!
Talk soon, John