Dear ABDEcon,
Focus on this part of your posting
they think I am qualified.
and then do your homework. Go through their website and learn all you can about the institution. If they think you are qualified then you probably already know what you need to do. Once the happiness/anxiety shock wears off, you'll do well. Congratulations on getting this far. Let your eagerness show but temper it so that they don't think you are desperate. Best of luck.