L3nny has pretty much summed it up. It's a good idea to tape up your headlights, cover your speedo, and remove your indicators but by no means essential. Do remove your mirrors though or fold them in or tape them.
I prefer NoLimits trackdays and you'll find all you need to know on their website regarding tips to make the day flow nicely and the timings etc. It's a good idea to ask an instructor to take you around for a session, they'll show you the lines and give you some feedback. (NoLimits don't charge for this, don't know about the others).
Do not try to blast around like a hero. Remember there will always be faster and slower people than you on the track so do not feel pressured just enjoy it.
Do it!!!!
