Choir Concert Tomorrow

I'm really nervous. I got the solo part for Halo, but I don't really know how I'm going to end it, and I don't know the song in the middle parts that well so I don't think I can do it. I mean if I wasn't doing the solo with the mic alone then I would be okay, but I'm at the mic alone and everything I say/sing will be heard. I know I can do it, but I'm really nervous and I haven't ever sang in front of a large crowd with a mic...so hopefully she will let me practice before...I'm going to freak out. Ugh.