Be confident but humble. There's a difference between the two, and interviewers can tell the difference. (Hell anyone can tell the difference. Nobody likes arrogant @#*@s anyway). Show your strong interest in the school by asking the interviewer questions at the end about how they like it there, what advice they would give someone who wanted to go there, etc.
They may not know anything about your stats, what you did, etc,--- but that may be a good thing. When they see you, they are looking for someone THEY would want to go to as a potential colleague, a future physician, whatever. Be confident, smile a lot, and listen well. I think that's really all you need to worry about. Honestly, don't overthink it--just relax.
Finally...sure, you may be into medical school, and that's amazing and wonderful (congratulations!) but remember that the most difficult part is getting to where is a good match for you. If they ask you if you got in other places, tell them that you strongly prefer MD schools, and are looking for a school where you think you'd be happy. (I.E. THEM). I'm into medical school already, too, but if people ask me, I'll tell them it's all about fit and location. (But also a relief to know that my dream will come true no matter what). Good luck!
