I don't think it will hurt, and I think it will be well worth it. Prep courses give you lots of practice material that is similar in difficulty to the real exam, and they help give structure and focus to your studying. There are very few people I know of that didn't take a prep course and were happy with their scores, and there are very few people I know that have taken a prep course and weren't happy with their score.
I took Kaplan and they were very flexible and had some students in a similar position to yours. If the class starts in Nov, you'll probably have covered the first parts of review as your first semester of Bio/Orgo will be almost done by the time you have those review sessions. Also, I know every college is different, but the amount of anatomy/physiology on the MCAT was way more than in my intro bio courses; so some of the things we reviewed in class I was seeing for the first time. The Kaplan course I took also allowed us to mix/match sessions with other courses that started later. For example, if there is a Mcat course that is starting next Jan/Feb, you can skip a Bio or Orgo review session in your class and take it later with the course that starts later, if you haven't covered that material yet in your classes.
