Wise words so far from everyone. Instruction is such a must so 100% book 1 or 2 sessions. Let the instructor know you are new to this as they will likely spend longer than the usual 20 minutes with you. I did Spa for the first time this year and ended up spending around 2 hours with the instructor which was a god send.
As for tyre gauges, make sure you spend money and get a good one as a lot of bad inaccurate ones out there. I found out recently at Combe that mine is crap but my Michelin foot pump is dead accurate. Turned out a lot of people's at Combe were the same and my foot pump become the most popular item
The brake comment is so important. After a run, do not touch that handbrake or sit with your foot on the brakes. You will coat your discs with brake pad and warp your discs. As said, cool down lap, into pits, stop car, engine off and leave car in second.
Check your oil throughout the day and take spare with you.
Check wheel nuts throughout the day.
Check tyre pressures. After a session, hot they should be pretty much at the manufacturers recommended levels or a little lower depending on track temp. So you will need them set lower when cold.
Enjoy it and remember to have fun.