Thank you all for your help. It's 2am here, but I've really had a blast and I'm delighted to say that it looks like it's basically working now. See photo attached. (I need the proper dimensions for the paperwhite -- what are they?)
What I did:
I used this tutorial a bit
https://gist.github.com/TobiasWooldr...ca75190b9a473f following it just far enough to get USB mode (from the diagnostics menu), and then the Kindle appeared like magic on my computer desktop as a mass storage device.
I'm afraid earlier I also played around with all things wifi-related, and have now caused the kindle to spit out a bunch of error messages into the terminal every 15 seconds or so, but if I ignore it it's fine.
I'm going to load up a nice collection of family photos as PNGs tomorrow, and pop them into the screensaver folder, replacing Amazon's ones. Then I'm DONE. No need to jailbreak or whatnot. I've had my fill for this week.
Thanks so much again for all the help -- seriously, very much appreciated!!
