Well first off Welcome .. and secondly .. don't be nervous and just be honest with them. If you don't understand something ask .. and if you aren't sure how to answer something say so ... they will ask you in a different way so you know what you are saying.
I was a little stressed about mine too. I was sure they were going to label me crazy and I wouldn't be able to get the surgery.
But the Doc was very nice and just wanted to make sure I understood what the surgery was about and that I didn't have false perceptions.
Good luck
