Don't waste your time studying too much. The exam is very basic. Anyone who is currently practicing medicine in a residency program should have very little trouble passing if you are reading and keeping up in residency. Of course, a little review is needed in areas not covered in your particular residency. Certainly, though, I don't think you need to spend $1500 the first time you take the exam. Try a $20-30 review book you can find in any Med school book store.
On the other hand, if you have been out for a long time practicing in another country and are trying to pass the exam, it may be a good idea to take a review class so that you learn the US way of medical practice. Anyway, I hope this helps. Again, I wouldn't stress over this exam. Parts 1 and 2 were much more difficult.
