Before you do a trackday make sure your car is in good working order. Change all the fluids (gearbox, engine, radiator, Dot5 brake fluid).
Make sure you have decent pads as well (something like RB74's not your nissan oems).
I did my first trackday over 6mths ago and im still repairing my brakes now. I destroyed my master cylinder, glazed my pads and seezed my pistons. Now almost $3,000 later and she's almost back to normal.