For anyone who finds this thread with the same questions I had, here’s how it all worked out.
Based on the feedback I got here, I ordered the Editor for Cubase, which was a download. It is in fact dual language Japanese / English and since I bought it from the US site link from Romantique above, it defaulted to English when I ran setup. I’m returning the standalone version I ordered, unopened, as the Cubase editor is nicely integrated so there’s no need for the other. A $5 learning experience for return shipping, which I can live with. The Cyber Diva voice bank shipped from Japan and will be here next week.
There was initially an exception thrown when I ran it due to the need for a couple of KB patches to Windows 7 detailed on the vocaloid site. Once I installed the patch and the Daina voice bank library, everything came up and is operating as expected.
Thanks again for the help on this, guys. Now comes the learning curve.