This is a partial guide mostly dealing with the wiring.
First fully roll down the window.
After removing the door panel, tie a pull wire to the side mirror harness.
Unbolt the 3 bolts holding the mirror and squeeze the plastic clip holding the mirror.
Plug the mirror and wire harness out and leave the pull wire around the metal piece.
Remove mirror as down on the workshop manual here: OUTER MIRROR GLASS REMOVAL
Run 2 wires along the original harness.
Back of the harness from the mirror. Note the location of the clip on the top. You want the top right empty slot.
Find a old floppy connector from a computer power supply and remove the connectors.
Push in connector into the empty spot referenced earlier.
.110" female quick disconnection used for connection. Connect the new wire to either connections. There is no polarity so doesn't matter which one.
Should end up with something like this.
Installation is the reverse of removal.
Used one of the bolt on the left for ground.
Test for voltage when rear defroster button is depressed. Should heat up fairly quickly once installed.