1) Get in contact with Hoofprints in the Sand. She may be able to help you. She is in Ohio and goes to mini trials in a series. www.minitrialseries.org
You should go to www.useventing.com
to see the USEA recognized horse trials in the area
2) you can find the actual dressage tests on the USEA website. Dressage is mostly just basic walk, trot, canter. Mostly trot. 20 meter circles and one half circle is the norm. As far as jumping, beginner novice is very inviting. very little scary stuff usually. And under 2'6"
3) Definitely work on dressage. Nowadays, dressage is the killer. You can almost never do well as far as placings if you don't get a decent dressage score. Work on smooth transitions and full 20 meter circles. And using your corners. As far as jumping, get used to jumping 2'3" to 2'6" courses (about 8 to 10 jumps) including brick walls, gates, flowers, and oxers. And practice cross country this spring if you get the chance.
4) Make sure you are ready. Eventing can be overwhelming to someone who is not prepared. But if you are with a good trainer and you are on a good, cooperative horse, you should be just fine
the most important thing is to not lose sight of why you are there- you and your horse. Don't worry about anyone else.
Have fun! and I look forward to hearing about your eventing adventures! It's addictive!