As opposed to directly heating the solder and pad directly use a desoldering braid and it will wick the solder away without damaging the pad. You can then easily remove the old switch clean the pads with the braid and the iron. The PCB has holes in it to locate the switch so place the new switch and add a drop of solder to your iron and just tap it where it you need it, it hardens almost immediately.

If you use the Omron D2LS switches, there are two models the D2LS-11 and D2LS-21. They both fit, but the click pressure is different on the two. If you want a firmer click go with the D2LS-11, but if you like the original feel go with the D2LS-21.