Most of these questions can be answered from searching the forum.
But, in brief - no, you'll need to download it elsewhere (I strongly suspect). I haven't heard of anyone previously downloading it on their computers. (When I took the original SCEA, I actually had to buy my voucher from Sun directly, rather than from Prometric.)
My understanding of the current requirements is that you have up to a year to submit your Part II assignment. (Which, IMHO, should be far more than enough time.)
You submit your completed assignment directly through the website, not via the test center.
Theodore Jonathan Casser
SCJP/SCSNI/SCBCD/SCWCD/SCDJWS/SCMAD/SCEA/MCTS/MCPD... and so many more letters than you can shake a stick at!