Keep a copy of all the device specific numbers.
You may want to transplant those to the motherboard you buy.
(The idme command can write them into the motherboard for you.)
That will also cover you in case the board you receive happens to be blacklisted.
And once you get it running again, jail break it before it can connect to the Internet and update.
Once jail broken, make a complete backup:
https://www.mobileread.com/forums/sh...d.php?t=289690
That backup routine is the only way you can get a proper version, matched pair, of diag kernel and diag filesystem for the device. *
Amazon does not include those in the full update image files.
Put those files in some safe (not on the kindle) place for the next time it breaks.
(*) And for all the people who have asked for it, and all the people who should have it, I find it hard to believe there has only been 16 downloads.