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It would be best if you wire into the fuse panel, hard for me to say if everything would work tapping into the current wiring for the lights, you could draw to many amps if you add to many lights in the cabinets. I would run the wiring to the fuse panel, many times you will have a blank spot for a fuse, I would see what the other lighting is rated at and use that same rated amp fuse.
I only know a little on the dimmable lights and they normally only work good with LED lights, you can get a 12 volt controller to make that work, click HERE for that. So you would just replace that with the switch but you would need LED lighting for it to work properly.
Yes if you have fiberglass siding it would be like doing a boat, same method for buffing......
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