Jean,
If the only wire that's bad is the foot controller wire, then it's an easy fix. Just pay attention to where the wires are connected and put the new ones where the old ones were. It's that easy.
Of course I could go on to say that I make the little rings on the machine end from the cord wire, and solder them so the screws hold good, or I could say I solder the connections on the controller ends for good strong connections too, but I've said that before so it would be repetitive ...... oops, I did it again .....
Joe