My First OR Day.... I'm Freaking Out!

Hello everybody. I'm in my first Med/Surg rotation and I found out that tomorrow I am supposed to go to the OR to observe and I am scared out of my mind. I read the post on some helpful tips for observation but I still have a lot of questions. I was told by my professor basically "Come in tomorrow with your street clothing because your going to the OR and you can change there" and she told me a chapter to read in the book which gives you a basic overview about OR nursing. I'm worried because I am a pretty big guy and what happens if they don't have scrubs to fit me? This is only my second clinical even though most of my classmates have had at least two more clinicals more then me so I feel like I am not going to know everything that I should know going in. I'm really excited to get to go into the OR I just don't want to screw it up and I will be really embarrassed if they don't have scrubs big enough for me. One of my friends told me that doctors actually cath. themselves if they have a long surgery. Is that true? I'm sorry I sound frantic but I'm just not sure what to do and I don't want to look like an idiot or screw this up.

!Chris