Most of the other threads seem dedicated to other Boox devices, so I'm back on this thread. If anyone stumbles on this thread with a cracked screen and needs help...
I've successfully replaced the screen and without much effort, but taking a pic of the guts before dismantling it was a life-saver.
Here is the replacement screen - the only one I could find that had the proper LED backlight connector - but I couldn't get it to fit, so... I might as well have just gotten the cheapest ED060XC3 (the same as the Kindle Paperwhite). I just carefully removed the old LED backlight strip and attached it to the new screen.
Attached is also a pic of the guts if anyone is interested. Note that the back cover just snaps on and off and I already removed the battery.
I thought I read somewhere that e-ink display batches had different voltage calibrations. I don't know anything about that... I replaced the whole thing in about 30 minutes and it works great again...
The lady will much more careful with her book, now. I've ordered her a
Duragadget case, as well.