I agree with coolrunner. Take it at your university, try your best, and maintain a close relationship with your professor. I took biochemistry about 2 years ago at my university and got tutored by a student who took the class a few years before. Also, if you can, try and find some students who already took the class and get their tests if possible. It will give you an idea of what kind of questions the professor will ask. I am currently taking O chem 2 and have all the professors quizzes and exams from a few years prior and I glance over those. He even uses some of the same questions.