I took this test twice, passed the second time. The first time I failed it by 1 point. Let me add that I am an adult student who had not taken Biology previously, but like you, needed Bio. The first time, I used REA Bio and a college Bio textbook. The REA book is a good outline, but very condensed. I found the practice tests to be much easier than the actual CLEP test. I had a false sense of security with REA Bio because I had passed a few other CLEPs using REA. The second time I added instacert and Biology24 videos. Instacert helped me to remember and understand the vocabulary better and Bio24 videos helped me to understand entire processes and relationships of systems.
Both tests included a broad range of questions in all chapters of the REA book, and most questions were different between the two CLEP exams. Test questions are all-encompassing. Questions like animal cell vs. plant cell, what is the difference? 1.2.3.4 your answer options are combinations and you have to pick which one is correct. Another would be respiration system, put the words in order. A few questions asked which statement is correct or which statement is wrong. A few questions were gimme questions similar to REA practice questions. The test goes over DNA chemicals and process, enzyme reactions, chemical bonds, molecules, chromosomes, alleles, Punnett Squares, Hardy-Weinberg equation, reproduction of plant cells and animal cells, detailed stages of mitosis and meiosis.. I could go on. Both times I was very pressed for time, so if you don't know it, mark it and move on. Go back to the harder questions later.
If you can pick up a Bio book, read and understand it, know how to take a test, you should pass. I went in the first time around not knowing what I was getting into and only missed it by 1. If you can't, I would recommend studying a little more because having to wait 6 mos between tests sucks.
I hope this helps.... Good luck to you!! and anyone else looking to take on this exam.