My first time out, I was totally lost through most of the first song. This was a song that I had practiced to death and knew frontward and backward. And I just was LOST. Second song I found my footing and never looked back. I even have a video of that first song, and even though my head was exploding, it doesn't come across so bad. So while I hope everything goes smoothly, even if it doesn't, have a short memory and keep plowing forward.
Secondly, think "excited" over "nervous" - it's OK to be excited, and you can even use that to your advantage when playing, rather than thinking about it as nervousness. Excitement brings out the best in you.
Best of luck - you'll be fine.