I believe that this is what you're looking for .
iFixit says: "The MacBook Pro 15" Retina Display Early 2013 packs the battery, keyboard, trackpad, and upper case into one assembly. If any of these components fail, the entire assembly must be replaced. Use this guide to replace your upper case assembly."
That's why I consider keyboard only replacement on these, and other machines, masochistic (and describe it as such to those who ask about "keyboard only" replacement).
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