The keyboard in the laptop is part of the top cover.
I’m not sure whether you can successfully separate the two to replace the keyboard, as I think that you may have to “break” the tabs that hold the keyboard onto the top cover.
Here’s a link to the service manual for your laptop, taken from this web page which may be of some help.
Scroll to p.29 onward to view the necessary pre-requisite steps and then the procedure to remove the keyboard /top cover.
Once you have access to it you may be able to determine if you can successfully replace just the keyboard only.
On p.36 it details how to remove the Power button board.
Once you have disconnected the board cable from the motherboard, use an Ohmmeter to test the button for continuity.
If the button is faulty, the part number is at the top of the page.
Search online using the part number (792777-001) only in the search box of your browser, to get results for suppliers of the part