Imo just don't go too overboard. Expecially if its your first race. You'll spend too much time worrying about your setup and not enough time thinking about the race itself. You'll learn things as you go along. You have a good grip on what you need to do to be ready, just have some extra parts on hand, just in case. Even if you don't finish, don't worry, many great drivers have had races they didn't finish, its all a part of the process. Just go out and have some fun and let things happen as they will. Of course don't go an neglect your equipment, but i don't feel as if you are the kind of person that would do so. If you feel your diffs need rebuilding and refilled, then do it, but you don't need to do it every race you plan on entering unless its some super huge event where getting noticed for sponsorship could be in the balance. Just make sure your rig is setup how you want it. Put down some good practice laps when you can and enjoy yourself. Anytime you make something your job the fun tends to get sucked out, make this your time to have fun and you'll always enjoy your time at the track.