When you change the headlight, be aware that you have to remove a bumper support from the bottom of one and fix it onto the new one. It is riveted onto the old one, so you need to drill out the rivets.
Also, when you are changing the bulbs, bracket, etc. over be very careful not to scratch the new headlamp - been there, done that! Have some Meguiars PlasteX (PlastRX?) on hand, just in case.
Before you remove the diffuser, spray some WD40 on the two most forward (furthest under the car) bolts - I managed to shear mine off and had to remove the brackets, grind off the remainder and weld in new bolts (well I didn't, but my friend Paul the technician did, while I watched). Also be careful with the various tabs that slot into the bumper, they will be especially brittle in this weather.