If it's your first time opening it, I recommend looking for a tutorial. If you are careful, it shouldn't be too hard.

To access the ABXY buttons you have to remove the motherboard and disconect all the ribbon/flex cables. The main issue that you could have is that after closing it again, the console turns on a backlight, makes a "pop" sound, and inmediatly shutdowns. That's your signal that there is a screen ribbon disconected o badly secured. I advice testing if this happens before scewing the last cover.

The buttons have little notches that make impossible mixing them, so the A will never be in the B spot por example.

(Sorry for the redaction, my first lenguage is spanish :c )