I've taught this class to people who failed the test previously and had them pass it on the last day of class. One of the big "gotcha"s is understanding the parent-child thing about replica placement. If you don't have that down pat, I can promise you won't pass the stinker.
Do you understand how subordinate replicas get on servers? I've known some really good admins who had never had this explained to them and, as soon as they understood, they ran their networks better AND passed the test.