I'm kinda new to this, so let's see how much I fail:
How hard was it to replace those rockers?
Unfortunately, I didn't do a lot of the work on the car, as I was enrolled in online college classes at the time (DARN YOU COLLEGE!! -Shakes fist-), and didn't participate in the installation of the new rocker panels. That'd be a question for my dad, Haha! What I do remember, though, is that the new panel needed to be cut to fit where it needed to go. As the GP was an SE, and didn't originally have the ground effects, we made the holes and installed the hardware needed for the moldings to sit on the car.