Interesting they've still got them! The prelude disc actually wasn't a preorder item, but it was supposed to only ship with the first run of copies - like the Chrono Trigger DS CD. Glad you got one. I still need to watch mine.
The wi-fi quests are pretty straightforward to download, luckily. I think the menu translation blog covered them at one point.
PS - let me know if you ever figure out what the greyed-out quests are about. I'm still trying to figure that out.