your goin to have to get turn,running, and power for the heat out to each mirror.
the connections, is up to you how you do it. i went to a bone yard, and got the door plugs from a 05, cut my door plugs off, put those on, and ran my new power wires to that plug.
or, you cut the plug off your new mirrors, so you can get access to the wires, and just splice them all together, solder and heat shrink.
the power for the heat, you either put a switch inline, or a relay inline. if you use the relay their hot all the time, the switch makes it user selectable. i used the switch, and it should be noted, use a lighted switch, and put it somewhere you can see it getting out of the truck. i have forgotten to shut them off, and came out the next day do a dead battery. i might put a key on relay before the switch in there someday.
as for where to get power for heat, thats pretty much anywhere. turn, you can get that from under the dash if you want. there will be turn and running you have to get to the door. i went under the brake master cylinder, and tapped into the wires that go back to the trailer plug, not the truck. this way, if i was having problems with the lights on the trailer, i could simply turn my lights and turn signals on, and look at my mirrors instead of having to check all the fuses.
if you use that 4 wire trailer wire, it makes running the wire easier as everything is together already, and lets you color code easier under the dash.
take a small piece of reasonably stiff wire, like electric fence wire or welding wire, and run that through the rubber boot on the door, and use it to pull your new wire through.
