As the pad goes between the seat fabric and foam there is very, very, very little risk involved in adding the element, moreso in that there are OEM seats that contain a heated seat element.
Obviously, take extreme care not to knock loose any sensors or pinch any existing wires.
That said, I finished my install today. Pretty straight forward, read the whole how-to here: http://www.focusfanatics.com/forum/s...32#post4456132
For power, my 2012 SE hatchback has existing fuses on the rear fuse panel for heated seats (both are 15A). I simply tapped those for power and ran the wires down under the door sill trim.