Bumpers will need removing drilling out the holes where marked up and then the wiring will need feeding through the car and wiring up so can't be that difficult as long as there's some form of guide as I've fitted at least 50 maybe more to ford's and one to the front which nearly became a disaster as they don't have the hole markings
did it and worked fine though
2010 focus bloody wanted front and rear sensors and that was my first attempt at the fronts as there was no one else who who touch them at the place.