My thoughts for Part II:
The biggest advice that I can give you is that you should design the assignment as an architect.
don't put much details on your diagrams however, write down all your decisions.
For example for each diagram (class and component) I wrote a my decisions.
Some questions that you could answer in your comments:
Which patterns are you using here? why this pattern? is it scale? why this persistence mechanism?
One more thing, sequence diagrams are about 10% of the whole exam so don't spend much time on it.
Start creating a consistent class diagram (extending your business model) and then your component diagram (how your classes interact themselves).
My thoughts for Part III:
It is by far easy, you just need to know what you've designed.
The decisions that you've wrote down on part II will help you a lot.
Before take the exam just print out your assignment as well as your design document, read it a few times and that's it...
Websites that helped me a lot: https://coderanch.com/forums/f-26/java-Architect-SCEA http://iamin.blogdriver.com/iamin/208073.html http://www.google.com