After my first day, I thought there was no way on earth I could do this.
Luckily I had to go right back out there the next day and do it again, and halfway through I realized it was fun and I started to feel like I could do it.
You're no different than most of us. This can be done, but it's not something most can just jump right out of the box and do well the first time (sometimes the first several times).
You can help yourself out a bit by taking care of some little things that you can control and build on:
1-Above all - RELAX. It shows.
2-Look the part (right uniform, looking good, shoes shined, etc.)
3-Be early (it impresses the administrators)
4-At least be in correct position - that's part of the battle right there. Know where you're supposed to be and when and be there. At least they can't say you're out of position.
5-Mechanics - take your time and signal correctly and slowly, you'll look like you've been doing it for longer than you have.
The other stuff builds from there. You can read the rule book, but rules sink in when you apply them. They
really sink in when you get them wrong.
Hey, I've only got 19 more games than you, so I'm no expert. But I know what it took to get in my personal comfort zone. The fact that you care enough to want to improve is a good sign.
Above all - have fun. Remember, it's not about you. It's about the kids. Enjoy it. Don't give up.