Novice days are far from being just for shitty and inexperienced track drivers,from my own experience,a high percentage of drivers at Novice days are far,far from being anything of the sort!
I'd recommend a Novice day for a first timer,as a well organised day will give you the opportunity of going out with instructors who are well versed and experienced of driving the track you are attending,and will give you masses of good tips about how to improve your day to day driving,along with how to apply that craft on track.
We all think we are driving Gods,but go on track with a good instructor,and most first timers would change their opinion,and recommend the same to others (doing a Novice day first)
Helmets are generally always available to hire on the day (£10.00),and I've never felt the need to use anything other than the seat belts that come in the car.
I've never used track day insurance,however, I'm in no way suggesting that you should do the same,it's generally based on a percentage of the value of your car,but expect to pay anywhere between £2-300.00 for a day's driving.
If you follow the instructions at the briefing,and drive within your limits,pit regularly to let both the brakes and yourself to cool down,and you'll really enjoy it,let the red mist descend for any reason,and going off track is embarrassing,can prove costly,and could result in you being barred from the rest of the session.
Check out MSV,really well run outfit,with loads of days up and down the country,arguably more expensive than others,but I'd recommend them.
Full day @ Snetterton for Novices on the 3rd Feb for £59.00, absolute bargain!
http://www.clubmsv.com/car-home/novice-only