As far as removing them, it's a simple process. You can use fishing line or even dental floss (floss breaks easily and you need a lot of it) to "saw" between the molding's and the door to get them lose. Then it's just a matter of gently pulling them off. That's the easy part of course. Once they are off they leave a rectangular outline of 3M tape...and that stuff wants to stay there. The best way to remove the tape is with a 3M eraser wheel (which can be tough to track down locally...at least in my case). It's a drill attachment that uses a wheel to essentially roll the tape off of the vehicle. Be careful when using one because it can burn the paint if you're not careful.
I couldn't find a wheel around town, so I went at it like every other badge on the truck....with Goo Gone and my fingers. When I removed the badges on the truck I would liberally soak the tape and let it sit for about 30 min. Then I would use my finger tips to roll off the tape. This is the best way to do it without an eraser wheel because your finger tips wont scratch up the paint. This is especially important on a black truck. The only problem is that your fingers will blister and hate you. After spending a healthy amount of time trying to roll this tape off with my fingers, I realized that it just wasn't working as well as before. Like I said, this stuff wants to stay. So I soaked that stuff some more with Goo Gone and then drove to the nearest car wash. A pressure washer at point blank range peeled that tape off in nearly entire stips. It actually worked quite well.
Once the bulk of the thick tape is off the truck, you will still have a very thin outline of where the tape was. It's basically just the adhesive residue. A little 3M Adhesive Remover, a micro fiber towell and a little elbow grease will eliminate this. Goo Gone doesn't do so well with this thin layer because there isn't really anything for it to adhere to. Then I apply a polishing compound by hand to remove any fine scratching/hazing. Then a healthy coat of wax and you will never know they were there.
Once they are off the truck, you quickly realize that they are flimsy pieces of plastic that probably cost $10 to make. What a joke what GM wants for them.