How to replace the keyboard

Hi guys,

I probably need to replace the keyboard, as my child poured some water over it. Generally the notebook still runs fine, but after a while the shift and the alt-key gets kind of stuck, not physically though.

I already tried to remove the keycaps, but didn't find anything that would explain the fault. Now I want to try to replace the keyboard to see if it fixes the problem.

Would I need to remove the whole upper case to exchange the keyboard? Or is there a simpler way?