Hi Srinivas Karthik,
The prerequisite for OCE EJB certification is OCP JP (any version). Since you already have this certification you are eligible to take this exam. Yes, the preparation vary from person to person depends on so many factors (knowledge they have, grasping skills...etc). I recommend you to develop few EJB programs before starting your exam preparation. There are many free tutorials available on the web, go through them and start developing small EJB applications first.
For exam preparation I recommend epractize oce ejb training lab.