Cindy welcome,
Since this is your first CLEP and just to be sure and on the safe side, I would encourange you to go ahead and buy the REA study guide, I always use REA study guides where available it really compliments IC and kind of reenforce all the material from IC plus more.

Give you self a complete two weeks, then test yourself with Peterson tests then from there you will be able to tell whether you are ready or not.

Welcome and goodluck