I am preparing for SCBCD 5 right now. I have 6 months experience with EJB3. Learn as much as you can about JPA (there are three documents in JSR 220, JPA is one of them).
Read Pro
EJB 3 JPA by Mike Keith. Also, learn all the annotations that are specific to EJB3. Take the Sun ePractice exams ($55).
It will take you several months to prepare as I have a few years of EJB 2.1 experience.