Don't waste your time and money. The hands-down best reference is Sun's SCEA study guide. Study that and google the topics it covers and you'll be fine. the SCEA exam Part I will be a cake walk if you understand the contents of that book.
I used Whizlabs Simulator and though it was far from perfect. There are some questions that are ambiguous (or just plain wrong). It can drive you a little insane, but I would go for it. It helped me to just get in the right mindset before I took the real exam. I passed with 93%.