It can´t go wrong, you can experiment. If you see something isnt going right you can always reflash it to the original code. I myself customized it and added a debug flag and changed the buttons place: https://github.com/clockworkpi/Keypad/compare/master...Mihaylov93:master
Here you can find a tutorial on how to upload code to the keypad: [Tutorial] How to compile and upload code to the keypad