It just involves a drill, small file, screwdrivers and abit of tape, think I also used a skewer to help get the wire through the grommet in the bulkhead into the cabin. The hardest bits in fitting is the drilling the hole in the bumper (I didnt want to cut a hole in my nice new car) and pushing the wires throught the grommet but that was just fiddly not hard.
Their is a link in the other post which has a picture in it of the hole that has to be cut in the bumper. The instructions are very good it involves lots of pictures aswel which is handy.