Just put in seat heaters over the weekend. Mounted the switches into the center console below the shifter. The seat backs are connected by a J-clip that you can separate using a flat head screw driver. The seat bottoms are connected with hog rings. You don't need to pull the entire upolstery off, just enough to get the heating pad on. There is also a metal wire on each side of the bolster underneath that you need to disconnect the the seat backs, and a row of hog rings on the first seam of the seat bottom.
The first side took me about an hour, the second side took under a 1/2 hour. My focus already had a fuse for seat heaters - #52 I think, that I tapped in for power, then grounded on a frame bolt near the fuse panel.