I rooted this unit, and through my own stupidity (and curiosity!) managed to corrupt the onboard storage to the point where the unit would not even boot past the initial bootloader splash screen. The Fire HDX is notoriously hard to manipulate via android ADB if you can't get past the bootloader, so the only other option was to replace the entire motherboard!
The Kindle Fire HDX models are a nightmare to service but with lots of patience and careful prying I was able to get the it apart without damaging any components. I was able to swap the motherboard and reassemble the unit. A quick battery charge and it started right up! All the peripherals are functioning as well.
Patience, patience, patience! There are many opportunities to break this thing if you are not careful. Slow and steady is the only way with these tablets. Amazon did not want to make things easy for DIYers! A phone/tablet screwdriver and prying kit is a must. Initially pulling off the top plastic cover has the potential for the most damage.