Panasonic KXTC1870B phone. My number 4 on the handset stopped working.
Panasonic lists, among 100 other parts:

QSX10108Z KEYBOARD SWITCH 3.60
PQSX10091Z KEYBOARD SWITCH 4.41
PQSX10092X KEYBOARD SWTCH 12 KEY H/S 4.93


so I wonder which I need and does this require soldering? I can rip
stuff apart no problem but was just wondering how much a pain this is.

It took forever to find a phone with the features I need and it's only 3
yrs old!