I made the Incredible task of replacing all face buttons and shoulder buttons of my 3d, for anyone that is in fear of doing it, just follow the ifixit instructions with some videos and you will probably be fine, but I will say, this is not an easy task, specially if you remove the upper screen cable by mistake ;-;
(another tip that I have is to take a photo of the motherboard before doing anything, so you can remember what is what when you start to reassemble everything…)
Posted by Emotional_Boat8231