yes and no.
plan carefully and establish the routines on the first day. spend the first couple weeks reinforcing the routines, and then the rest of your year will be as easy as you like.
it is normal to be nervous about the first day (even if it isn't your first year). you'll be meeting a whole score of new people who are going to be looking to you for guidance. they'll want to know about you. who you are, what you're about, and how you're going to treat them. be prepared with a little monologue about you, and take some time to have the class introduce themselves as well. this is a great way to foster a positive classroom climate.
btw, the students are nervous too! they are probably even more jittery than you are (hard to believe, i know). knowing that helped me to realize that the first day should be a time to set them at ease by getting to know them.
for more info about the first days of school, visit [url]http://teachers.net[/url] and read thru the articles by Harry and Rosemary Wong. this will help you plan for the first day to make your year a success.
take a deep breath and try to relax!