Being from OOS, expect to be grilled about why you want to go to Wayne State. They are looking for people who want to be doctors and remain in the Detroit area, or at least in Michigan, so have a reason or ties to the area to discuss. Depending on your interviewer, you also may be grilled about why you want to work with disadvantaged populations.
Other than that, the interviews tend to be very laid back and conversational. You will be more likely to be asked "tell me more about X in your activities" than you will be asked challenging interview questions. Relax and be friendly, and know something about the school, and you should be fine.
For transportation, you will probably want to rent a car since public transportation sucks in Detroit. You could probably manage without it, but the busses are not something I would rely on, and a cab would be about as much as a rental car. You will be flying into Detroit metro, and it is a straight drive down I-94 from there to get to the city and the med school campus.