Get there early and if possible, maybe check out the area the night before so you don't get lost...not that it's hard to find or anything, it's just better to be safe than sorry. They'll sit you in a room with the other applicants and provide you with food and drinks.
As for the interview, relax and be honest. The UIC interview was very conversational and laid back. With both of my interviewers, we ended up going off topic once we found some common ground (bartending, same alma mater, etc). The interviewers are required to ask certain questions, so between the conversation, they'll have to look at their Q sheet and throw out some of the classic interview questions...Why dentistry, Why UIC/Chicago, etc.
As an out of state applicant, I would have to same your chances of getting in statistically aren't too high. The past couple years they have admitted a very select few, if any, out of staters. They usually max out at about 6 out of staters on the higher years, but who knows. If you're competitive and an all around solid applicant, you have as good of shot as any. They obviously liked you enough to give you an interview.
Best of luck.
