They're fairly simple once you gain access to them.
Open the door, remove the 3 Phillips head screws securing the panel that holds the coin equipment, being careful to not let it drop, as it could damage wiring.
Once that is out of the way, you'll have room to reach the button switches.
Depending on which style of buttons and switches you have, the switches either slightly twist off or just pop into place via friction.
Carefully pull down on the switch assembly (or twist it a quarter turn) and it will pop free from the button assembly.
Next reach up to the underside of the button housing and unscrew the jam nut holding the button to the panel. Buttons pull out from the top.
Assembly is in the reverse order. Make sure you orient the button correctly, some will have pins that protrude from the bottom to keep the button from spinning in the panel.
Hope that helped.
Good luck, Curtis ash100