You pretty much have to remove everything to get to the keyboard. Once you get there, there must be 40 to 50 tiny screws holding the keyboard into place.
Unfortunately there are no videos for the actual keyboard replacement, and in the comment section of the general video above, it is actually mentioned that it would be quite hard, for a reason I was about to discover.
Once you remove all the screws around the edges, the ones holding the 3 metal plates on top of the keyboard, and a few on the back side, you realize that keyboard is still firmly attached.
There are actually about 17 screws that are under the black plastic sheet that covers the back of the keyboard. Accessing these requires to separate/lift the black plastic backing from the keyboard.
You can practice doing that carefully on your bad keyboard so you can be sure not to damage the new one when doing it there.
The best is to use an X-acto blade, start at the bottom left, work your way up the left side, then across the top, then down on the right. Put toothpicks as you move around so it does not glue itslef back.
Leave the bottom attached as this is where the connecting ribbon comes through, and it will serve as a hinge, so you can lift the black sheet and the transparent plastic open up while removing / attaching the screws.
As you lift the back on the old keyboard, take note of which screws are attached in that layer. I suggest lifting both the old and the new keyboard sheets, and using a magic marker to circle the screw locations on the new keyboard.
Once the old keyboard is removed, place the new one in, keep the backing lifted with something while you put the screws in the marked locations.
Then reattach the backing, pressing down around the edges. Then proceed with putting in all the screws around the edges of the keyboard as well as the few that go on the back between the plates.
Notes: Take pictures of the keyboard before removing any set of screws so you can be sure of where they go!
Then put back the two plates on each side.
The large middle plate goes on top of the two connector ribbons (a narrow one and a wide one).
Here I had some problems I want to report. The connector ribbons are a bit longer than necessary. On my original keyboard the extra length had been made to buckle at the top under the connector. So I initially did the same on the new keyboard. But the new keyboard ribbon was more rigid at the top so the buckle was not forming very well. When I placed the battery above that, and tested the keyboard, it was malfunctioning. Several keys on the left side did not work.
Note:Don’t reassemble everything right away. As soon as you have the keyboard and battery in, start the computer and test the keyboard. No need to waste time putting in all the covers screws if you find out it is not working.
After some trial and error, I deducted that with this new keyboard it was best to let the extra ribbon buckle at the bottom so I could get a straight connection at the top. I pushed the connector deep in, clipped it, and taped it, so it would not move. Then mounted the middle plate making the ribbon buckle at the bottom (there is actually an opening in the plate for that).
Once I did that the keyboard functioned properly...
So replacing that keyboard is definitely no picnic, but is it doable with some time and patience.
I has zero screws left after reassembly which was a small miracle in itself