I just heard about that you will receive the assigment through e-mail message. I have talked to Sun Microsysystems
recently because I am going to prepared for do the SCJP 1.5 so she said to me that I will have from 10 to 12 months
for do the certification exam.
Maybe reading through the FAQ would answer some of your questions and maybe also some other questions you may have during the wonderful journey to become a SCJD
I will answer your questions quickly. The SCJD exam comes in 2 parts: the assignment and the essay exam. for the assignment (CX-310-252A) you pay the voucher and you will get an email with instructions where you can download your assignment. Once you downloaded your assignment you have a 12-month limit to complete the assignment. When you have finished your assignment, you have to request upload rights and then you can upload your assignment (at the same website where you downloaded it).
The essay exam (CX-310-027) is a written exam where you'll get 4 open questions (so no multiple choice like the scjp exam) about the assignment and the choices you have to make. The only purpose of this exam is to prove that you were the one that wrote your assignment (and not a friend or a relative who is really good in Java). So no material at all allowed when you take part 2 (because otherwise your friend or relative could write everything down and you just have to type out his notes)! If you have completed the assignment all by yourself you don't have to be afraid of this essay exam (it is really a no-brainer).
After you submitted your assignment AND took your essay exam the grading process starts. It takes 4-6 weeks before you know you passed (although some people had to wait a whole lot longer, for me it was just 4 weeks). This is maybe the most frustrating time of the complete certification process.
If you pass, you'll be a scjd. If you fail (nearly impossible with the great help of the JavaRanch community) you'll need to buy a resubmission voucher (CX-310-252R) and you'll get a (very) limited feedback about the reason(s) why you were failed. You solve these issues and you resubmit your assignment back (you don't need to take the essay exam again).