Seems like it may be useful to someone if they want to know what this entails.
Its not hard to do but there always is the risk of something going wrong so do it at your own risk though.
First you needs the pads which for whatever reason are sold separately and in packs of 5 each, maybe the other 8 will make good shruiken or something. http://www.geekbuying.com/item/Original-GPD-WIN-GPD-XD-D-Pad-Silicone-Pads-375593.htmlhttp://www.geekbuying.com/item/Original-GPD-Win-Silicone-Pads-for-ABXY-Keys-375592.html
Need some sort of clean area to work on it, preferably somewhere you can ground yourself to avoid the small possibility of damaging something and with enough space to take it apart with a small cup or something to hold hardware.
Obviously you start out with the 6 screws in the case.
No need for tools here, you can pry it apart with your fingernails, go all around and pop it apart, remove your sd card before this, it'll catch when removing the shell if its still installed.
Careful here because it is fairly easy to damage the fan switch ribbon cable if you aren't careful, remove that and the battery cable and get the bottom shell out of the way.
Take all the screws out of the motherboard minus the 2 fan screws, remove the antenna cables from the chip and make sure the antenna wire is removed from the metal brackets, I can tell you from experience they will tear if you don't.
To note those two screws in the middle above the label, make sure those are fully tight when reinstalling, they leave impressions on the battery as it is and if they stick out any they will dig into the battery which is very bad.
You should be able to lift the motherboard out of the case, if it doesn't budge you probably missed a screw, yes the rubber shells on the sticks will catch going through, don't worry about that and just pop them through.
Make sure they don't flop around on the ribbon cable either, those can get damaged somewhat easily.
Flip it over and you'll find what you came for.
Remove those and install the new pads making sure they are installed on the posts.
Now put everything back together in the opposite order and voila!
Farewell mushy buttons and hello crisp clickyness.