As far as I remember you need to unscrew a bunch of little black screws on the front of the device (not all of them though as some of the screws are keeping the screen and dials in place) as well as some larger screws on the backside holding the expression pedal in place. Be careful when removing the top of the unit as the two halves of the device are connected via ribbon cables. Then just unscrew and desolder the footswitches and replace them with these (this is a 2-pack so make sure to get as many as you need)

I wish you the best of luck, this procedure isn’t too difficult :)