My advice would be to do everything you can to prepare for the MCAT. Take as many practice tests as you can in as real of a setting as possible so that it will be familiar when you do the real thing. I would also say it is probably a good idea to take a Kaplan or Stanford review course. There are also study books available at bookstores that are a good place to start in terms of preparation. They also have practice test in them. I think you can also access practice tests on-line. My philosophy is that this test is a huge thing and the more time and preparation you an put into it the better, even if you have to pay a significant amount for help.
Do you know anyone that could help you study? If there is a Learning Center at your school they may be able to help you improve your test -taking skills or match you up with a tutor or study partner.
Don’t study the night before the test, that just makes it worse. If you haven’t learned it by then, it won’t help you to try and cram. Take a long bubble bath instead and go out for ice cream with a friend. Make sure that you spend time de-stressing before the test so that you don’t have it all built up to create problems during the test.