Rescheduling won't hurt your chances since you're already interviewing early. I reschedule my interview and it was in January and I still got in. Chances are very good if you interview here.
UNECOM isn't far from NYC. It's about 290-300 miles. I drove from Queens and it takes about 5 hrs. I can't comment on UMDNJSOM, but can tell you that UNECOM and Columbia Univ. are like the only 2 schools (more than Harvard, MSUCOM, Emory, Tufts) in the country to have the longest anatomy course (about 245 hrs long)....that means you really learn your anatomy which is essential in medicine. For comparison, MSUCOM only does 60 hrs and others typically do around 120 or so hrs of anatomy.
3rd yr rotation sites include Newark (along with UMDNJ's (MD prog.) sites, LeHigh Valley (Allentown), Upstate NY, Maine, and they are in current negotiations with UMass.
Hope this helps and hope to see some of you guys when you interview!