Like Crip said: do the prep course because they will want you to have it done before they send you to the schoolhouse for training. When you get here, if there is still a logjam at student company waiting to come over to the 18D course, then you will be selected to begin sooner if you have completed that course. So do the course b/c it is expected of you by student company and will help move you up in priority for getting enrolled (which means less time on landscaping details waiting for the next class).
But if you want to ACTUALLY prepare yourself for the course, then the absolute best thing you can do is find a copy of this book:
Essentials of Anatomy and Physiology, Third Edition, Martini/Bartholomew
Even if you can't find this one in your price range and you have to get an old, used copy of the second edition, do it.
That is the textbook that is used in Med Fundamentals, and you can do yourself no better favor than prereading that book - especially if you do not have a medical background. I am not kidding, you are pretty much going to have to know it cover to cover anyway. If you can preread it in advance - even if you don't fully understand everything you read - you will understand far more when you hear it again in lectures and are able to ask the questions you have.
I've given that advice to a lot of people starting the course, and I don't know of anyone that's taken it yet. But someone told me to do it, and I did, and as far as I'm concerned it's the best possible preparation for the course.
If that's out of your price range then I highly recommend you find a friend in SOCM who is done with MedFunds and who will loan you his book while you're waiting to class up.
It's not just about passing med funds (not a trivial matter in itself). It's about really understanding anatomy and physiology. The better grasp of the structure and function of the human body you come away from med fundamentals with, the more sense EVERYTHING you learn for the rest of the course is going to make. If you have a good grasp of A&P, everything you learn from that point on will reinforce and expand on your base of knowledge. If you take the road more often travelled here, and cram for the exams while putting minimal emphasis on really understanding the fundamentals, then each new idea that is introduced subsequently will be more difficult for you.
I'm beginning the last phase of the 18D course right now, and last Friday we had a lecture from one of the Colonel/Doctors here on anesthesiology. He closed that lecture with a review of pulmonary gas exchange, and at the end said he was about to give us the best piece of advice he could send us out the door with. "Go back to the beginning," he said, "and fill in all the holes - and dig deeper - into your anatomy and physiology. If you
really understand that, everything else is gravy."
I would do the prep-course to satisfy the Army. I would pre-read that book so I could become the kind of medic my team deserves.
FWIW