Surely someone has written a book (or blog) covering what to do & expect at an OTB tournament. Seems like years ago I saw one in the USCF catalog titled something like 'My First Tournament' or some such subject for beginners. Anything like that would be helpful.
Also, Winterzero's suggestion to practice writing your moves on a scoresheet (any cheap notebook will do) prior to the tournament is good advice. Win or lose, keeping an accurate scoresheet is a good habit to start. Deep concentration during the game can make anyone forget to write down a move or two. If that happens, quietly ask your opponent if you can look at his(or her) sheet to update yours. I have yet to encounter anyone who refused to extend that courtesy.
Good luck!
But don't jump two categories! In future, consider moving up one category. Your rating may take a beating by playing and losing to 1400s as opposed to 2000 rated players, but your chess understanding will grow.
This reminds me of a guy back in the 70s who was rated about 1350 and he would elect, tournament after tournament, to play in the Masters section.
He was typically the lowest rated player by about 600 points and of course he lost every game. I'm not sure if he was learning effectively from the experience; an 1800 could have given him very good advice and he'd have a chance for a point now and again.
On the plus side, in exchange for enriching their prize fund with his greater entry fee for their section, the masters and experts would always do a post mortem with him, and they encouraged him to continue playing with them.
I would have given him one bit of advice for free: Stop blundering! i.e. work on your tactics and calculation.
I wonder if that is practically inferior to whatever the masters imparted to him.