I did 'em on a 2011 MR and it was a bit of a pain in the butt to do myself but they all ended up okay. I didn't run into anything that required trimming, but there are a couple that you have to just force the screw through the splash guard/fender liner. Also had one pop clip on each side on the rear that wouldn't go back in (the one hidden behind the mudflap when the mudflap is in place). No loss there, just OCD annoying.
Oh and you have to remove the rear wheels to do the rear ones. Even an angled screwdriver won't be short enough since the screw itself fills almost the entire space between the rear fender liner and the rear of the rear tire. So have a decent jack handy, 'cause you gotta take the rear wheels off.
Btw, that video posted above made the install possible. The included photocopied paper instructions were cryptic at best.