Purchase Kathy and Bert's brand new book: Head First Servlets and JSP, read it as many times as possible, work out the mock exam at the back after your last read, purhcase JWeb+ v4 for more practices and then pass SCWCD 1.4 with 90+.
Absolutely. As with the other programming exams (SCJP, SCBCD, and SCMAD), we believe that preparing for the exam is one of the best ways to learn it! People who learn the topic without also preparing for the exam often *skip* important topics, perhaps learning ONLY what they need to accomplish some task.
This doesn't mean you must take the exam--only that it's almost always a good idea to use the exam objectives as a way to figure out what to learn and study.
In our cert prep book, for example, we assume that you do not know servlets and JSP (but that you are a Java programmer, of course). For a Java programmer, there is nothing seriously difficult about learning JSPs, for example, but there are a LOT of details and a LOT of different kinds of things to learn, some of which do not involve Java code (the JSP stuff). Oh yes, you also do NOT need to be a *web* developer or know HTML when you begin your studies for the SCWCD. You will need to learn a little during your studies, but many web developers doing JSP in the real world are using a development tool such as Dreamweaver, so that you aren't expected to be really good at hand-coding HTML.