Current SNELL helmet will be perfect
If you guys are newer to this or first timers I highy recommend getting there around 8-830. This will get you registered, prepped for tech, etc. You will have a much better experience if you aren't rushed. Plus with as long as the PCA course designs are you will want the extra time to walk the course a couple times. Find someone who you know/looks like they have done this a while and take a walk around the course with them. Experienced people have really interesting stuff to point out that you may have not noticed before on a course walk.
If you don't have magnetic numbers REMEMBER TO BRING PAINTERS TAPE or something to number your car. I have seen people printing numbers off their computer and tape paper in the window.....whatever just make it big and legible. If you aren't driving a Porsche or Mercedes you will be in "X" class.
As far as tech goes, they are going to look at the condition of your tires, maybe peek through your wheels, they usually torque your wheels, so if you are sensitive to this I bring my own torque wrench and do it in front of the inspector. IMPORTANT to note is that you have to have a battery tie down, they will check that the battery is secured in the car. They will take a peek at your helmet. It is also a good idea to make sure there isn't a ton of crap to fly around inside the car, it could be a safety concern/more or a distraction than anything.