I took a blow dryer, set it to high and warmed up the pads nicely for about a minute. The pads peeled off cleanly and retained it's sticky adhesives. Once the mirrors were replaced, I heated the pads again. The pad have not come off yet.and then have fun getting the pads to stick back correctly.
Since you usually have to buy the whole part just use an extension to get the nuts off. Reach in from under the bike. Use a flashlight if you can't see them.
Having a friend here helps, as one person attaches the ratchet extender from below, then the other attaches the ratchet and removes the nuts.