Hi Ramedeus, I think that having experience as a web developer may help you to SOME extent with this exam, but knowing the basics of RMI will help you more. EJB has virtually nothing to do with Servlets, etc.. apart from the fact that they can both be found in a J2EE app and may interact with each other (Servlet -> EJB).
I've done SCJP & SCWCD using the Head First books (actually SCJP was using the book that they had before head-first, I forget the name).
I have the Head First EJB book which I started going through a while back (must get back into it) and I have to say I'm found SCBCD study much easier than SCWCD. There are so many abiguities and inconsistencies with the SCWCD technologies that I found it difficult to remember things and got syntax confused (I still got a good score - but through a lot of hard work). EJB is much "cleaner" and easier to remember stuff.
I leant the book to someone who had never done EJB before and he also found it quite clear.
The Head First books are excellent, I like the style and I especially like that the Authors are so approachable on these forums and by email.