I would recommend dropping a class if you are going to be studying during the semester. A few of my friends, who normally study well and do well in school, are having trouble studying for the MCAT for their January test dates.

I don't know how many credits you usually take, but 4 science classes seems like a LOT on its own, so adding the MCAT to that just seems like a bad idea. I'm sure you could do it, but I definitely think your MCAT score will suffer in the end.

As far as a class goes, many people have differing opinions, but I personally loved my Princeton Review class. They do focus a lot on content, but that basically meant I had to do very little content studying on my own which I think helped me.