For the first time, I would keep it simple and only concentrate on a few things. Otherwise you may feel overwhelmed.
Review the rules of the road, the main ones being that a boat on a starboard tack has right of way over port, leeward has right of way over windward. If in doubt, give room, especially at the marks. It's all about fun, remember.
The start can be stressful the first time out. Rather than trying to hit the favored end of the line
just as the horn
goes off (where it is inevitably crowded), I would start by trying to find a less crowded part of the line
and try to hit it with some decent boat speed. It's okay to be a little late the first time out. And you will definitely want to start on a starboard tack.
As you approach the marks, discuss in advance with your crew what you are going to do at the roundings, who is going to do what, whether you are tacking, jibing, hardening up, etc...
Sorry if this is too basic. Good luck!
Oh, and I wouldn't worry about lightening the load or getting better sails until you have been out at least a few times. I raced a couple of seasons before I replaced my old rags. It's all about learning the ropes and getting comfortable out there. And by all means, if you can get an experienced racer on the boat with you, you should, but you should drive.