If you can use a DVM, you can have it rewired in no time. It is likely a simple SPDT footswitch, although some ‘fancy’ versions can have a DPDT to ground out the ‘unused’ output, reducing noise. If you’re keeping it, and want to get even fancier, a 3PDT switch can be put in, and the 3rd pole can add an LED with say a 470‎Ω resistor. Here is a simple drawing.

J1 is your input. J2 is output A and J3 is output B. S1 is the footswitch. There will be a common lug, and a meter will show which lug is active during pressing the switch. I hope this helps.