The car in stock trim is great for getting started on track days. One thing that stands out to me though is your exhaust - which decat and catback are you running? Most of the race circuits in the UK are under strict council noise regulation, and an unsilenced decat with a catback on RX-8s can put you over the drive-by noise limit at a number of circuits. Which circuit are you doing, and is it one of the days where the club will have some members going as well?
In terms of prep, you'll want to ensure everything is up to snuff, so check your fluid levels, and take spare oil at the very least. If you're handy with the spanners, then giving the car an oil change and a brake service will do you the world of good - lubricated slide pins all round and fresh brake fluid will do the trick. Seeing as it's your first time out on track, you're not likely to be pushing the car too hard, so if your tyres and brake pads are decent makes with plenty of meat left on them, you'll be fine - you can always uprate them later once you reach their limits.
On the day, be sure to keep your sessions short. 20 minutes is the generally recommended session length, with a warmup lap at the start and one or two cooldown laps at the end of each one. Don't go longer than this, otherwise you'll start putting extra stress on the car and yourself - it's surprising how mentally taxing your first track experiences can be. When you park up, leave the car in gear and don't use the handbrake - you'll probably weld the rear brake pads to the discs and you'll almost certainly boil your brake fluid, neither of which is a good thing. And be sure to get some tuition while you're there - it's often said that the best mod you can do to any track car is to tighten up the nut that holds the wheel
Remember, if you've got any questions or concerns, have a word with the organisers. Everyone attends the same briefing in the morning, and you can almost guarantee that somebody will get carried away on track and ignore one or two of the basic rules. The organisers are there to stop that sort of stuff, so don't be afraid to go and have a word if someone's behaving badly on track. They won't bite your head off for being a novice. Speaking of which, ask at the end of the briefing if they have any novice stickers, and if they do, stick one on the back of your car. That will tell the other drivers that you're new to the track, and they should give you a bit more room.
Most of all though, have fun. That's what it's all about, so have a nose round the garages, chat to some of the other drivers, and immerse yourself in it