Should be as simple as cutting the wire, soldering the correct leads to a micro port (why micro rather than mini, just out of curiosity), opening up the hole to the appropriate size where the cable used to come out, and mounting the port to the mouse chassis. The mounting would be by far the hardest part, because you wouldn't have a designed mount point. Don't know what material to suggest. My first inclination would be some form of epoxy, but if it gets in the port you're SOL.