Word of advice, SCJA is built for people just really starting with application development. It does contains minimum of coding, object-oriented concepts, some UML and also Java Platforms and Technologies.
This exam is NOT pre-requirement for SCJP. On other hand SCJP IS pre-requirement to any advanced exams SCJD/SCWCD/SCMAD. So you may want to directly jump on SCJP. No need for simulators just get your self Sun Certified Programmer for Java Study Guide and you have all that you need to pass exam