The link that F6B1911 posted provides great instructions on proper routing of your electrical lead.

If the old grips still heat, you should be able to turn them on, allow the contact cement to that holds the grip to the bar to warn, and tug and pull to get the grip off. If the grip is not being replaced, it should not be done this way because it can damage the old grip. But in your case, it's being replaced anyway. If the old grip will not heat, have fun

FYI ... new grips have a new feel and sharpness to the rubber and your hands will feel the difference from side to side ... so order a new set or just the one accordingly. You will also need a small tube of Honda Handgrip cement, and Isopropyl alcohol to clean off the old cement (local drug store).