I basically with everything that was said. I don't want to alarm or scare you off but there is a comment that should be made regarding whether to install a harness. It is my humble opinion that a harness and no roll bar is more dangerous than staying with the stock three point harness. In the highly unlikely but still possible event your car were to roll (e.g., going off track sideways and hit a rut), your body / neck is stuck in an upright position which is incredibly dangerous if the roof caves in. If your interest in a harness is to simply keep yourself more planted, there are things you can do with your three point restrain system (e.g., cg lock or pull seat all the way back, tug hard on the shoulder belt till it locks, and pull seat forward while maintaining the shoulder belt in a locked position). Although these methods are not as good at keeping you planted as a full race harness, they definitely help and will be more than adequate for a track day. I also strongly agree that you should consider ATE or Motul 600 brake fluid. If possible, upgraded break pads are highly recommended. After that, the car is very capable on the track in stock form. Best of luck.
Thank you for your help. I am going to pass on the harness but will take your advice for the stock harness into account. I will be getting high temperature brake fluid before the track day, but today I get tires! Down the road, I am sure I will be upgrading to some better brake pads and ss brake lines. As for this track day, I have already spent more than enough money and am sure my car is more than adequate for my level of experience.