If you missed the CLEP Chemistry by only 3 points (even years ago), I'd recommend that you start there. You had known enough to score an almost passing. You may find it easier to refresh your knowledge rather than learn something entirely new. With some refreshers and a little bit of new knowledge, you would probably be able to pass the Chemistry test.
Given this I'd have to say:
1) Buy the Petersons Chemistry CLEP practice test for $20 at:
Prep for the CLEP - Peterson's
2) Take the first, of three, practice tests. These tests are a little harder than the actual CLEP. Your goal is a 50% or higher. The first test will gauge where you stand. With this knowledge of your weak areas:
3) Get a study aid. Check out the REA CLEP Chemistry. REA does have a reputation for quality:
Amazon.com: CLEP Chemistry (REA) The Best Test Prep for (REA Test Preps): Books: Kevin R. Reel
4) Practice tests and review of the subject material. After working through the review, do one of the practice tests in the book. See where you stand.
5) Shore up your weak areas and take your remaining 2 Petersons tests, and also complete the 3 practice tests in the REA guide. The goal is 50% or higher on all of these tests.
With only missing the Chemistry CLEP by 3 points, I'd focus on it if I where in your position. You know enough to almost get you there.