Heh, looks like this ended up being a one person thread. After some more research I convinced myself that it was either a US or Canada firmware and that in any case, both of them required the same update. I mustered up the courage, did the manual update, had some heartstopping moments with a 0KB protected file randomly popping up, but in the end it looks like everything worked out. Only problem was that Sony Library started giving me an "invalid type" error. I then used the suggestions in this very informative post
and that fixed everything.
Now to load the PRS-505 with some nice ebooks