Yep - really just de-register it and remove your books and you are good to go as far as clearing your personal info off the Kindle.
I'm not sure about protecting Collections if you've done a significant amount of work there. I think that Amazon backs up your Collections and I know that there is a piece of 3rd party software floating around here "Collections Manager" or something like that.
Some people like to do a factory reset just to make sure.
Menu
Settings
Menu
Reset to Factory Defaults
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