You'll be fine. Just keep your confidence up, and put off any worrying til afterward. And be yourself - personality probably counts for a lot as well as talent if you've all got to work together (that's the edge you can control even if there's someone technically better [which possibility you're not going to think about anymore anyway...]). And don't forget to audition them too - they might not be good enough or nice enough for you.
Can't wait to hear how it goes.
Kristin