I have passed the SCBCD 5.0 exam toady with 93% marks.
My preparation includes - Three month of continues preparation - Book Head First EJB 2.0 by Kathy Sierra Enterprise JavaBeans 3.0, Fifth Edition by Richard Monson-Haefel, Bill Burke (Oreilly) - Used the simulator from EnthuWare.
Although EJB 2.0 is not required to appear in the EXAM for EJB 3.0, I purchased an go through that book. This book helped me in understanding the concepts very easily. Further I have the feel for both EJB 2.0 and EJB 3.0
As being a professional Java Developer, you can not say ya I know EJB 3 but can not work in EJB 2. Even you have to work on maintenances projects which were developed in older version. So you must have a feel for that.