Just thought I'd add a note here for those who search later, as I did this morning.
Taking the pillar off was actually pretty easy on my 2013 Optima SX, once I figured out how to do it.
First, of course, you need to pull the weather stripping away from the door sill to make some room for the pillar to come out.
Then you just pry a little bit until it pops out enough that you can see the two blue retaining ("Christmas Tree") clips. Those come out, albeit not easily, with a trim removal tool. If you aren't very careful, you'll pull the pillar away from the clip and the clip will stay in the car. This is fine.
Once you have those two clips out, or at least have the pillar separated from them, there's still another clip up top you have to deal with. You'll notice it has a lot of slack in it. Get needle noise pliers and turn the clip 90 degrees and it will pop right out of the pillar. Then it's easy to pull the pillar off.
If the blue clips are still in the car, you'll need to get them out with the trim removal tool and reattach them to the pillar.
Once you're finished with your wiring, put the pillar back in place, starting with the tabs toward the windshield. Once those are in the right slot, rotate the clip up, and reattach the 90 degree clip using needle nose pliers again. Line up the blue clips to the correct holes and bang the pillar with the palm of your hand and they'll go right in.
Much of this has already been said, of course, but I haven't seen anyone mention that 90 degree clip, so I'm thinking it might be new on the 2013s.
Like I said, just wanted to add this so that if someone searches in the future they might have a little more information.
