I would add to ckon's removal info what I think is an ideal removal tool. Metal vegetable skewers. They're long, thin, and strong enough to do the job. My thinnest screw driver still seemed too thick and in danger of cracking the rail cap.
I took off the rear caps to remove my cross bars. I worked one skewer down the outside (closest to you) base of the cap. Once you get it worked to the end, pry back and forth a bit to feel both tabs pop loose. Leaving that skewer in place, I worked a second one down the inside edge of the cap. I was only able to get the first tab to pop out here. Work the cap a bit so that the outside edge rises up a bit so it can't reengage it's slots. Remove the oustide skewer. Next takes a bit of force...working upwards and inwards to try to pop that last inside tab. Remember there's also a tab from the cap into the rail itself, so you want to pivot around the rail.
For my troubles, the first cap came off clean, but bloodied my nose...yes I was leaning over my work. The second, I broke the top rail tab off the cap. Both caps snapped back on fine, but they're a bit looser than they were before. Right now, I don't think it'll be a problem.
My dealer was useless. I asked if they could show me the roof rack installation manual so I could get a better idea of how to remove the end caps. Claimed there wasn't one. Funny, the roof rack is listed as accessory for those that didn't get one factory installed. Surely there must be an installation manual.
Brent