First, I'd probably send you to the SCJP Faq. You'll find many of your answers tackled there! Almost everyone starting out has the same set of questions, so we've put them all together to save everyone some time.
SCJP is the programmer exam, and has no pre requisites. There is also an exam called the SCJA, or Sun Certified Java Associate exam which deals less with harsh syntax and instead deals with a broader range of topics. It also has no pre-requisites, and can be throught of as the entry level Sun certification. Basically, SCJA covers more things, like Servlets and EJBs, but at a higher level. SCJP is very syntax/language focussed, and does not deal with broader subjects.