I haven't done it too many times, but it's not too bad. If I remember right, after taking the door panel off, and unbolting the window glass...there is a channel in the front of the door that unbolts, a channel at the back of the door that unbolts, and you need to take off the fuzzy strips along the bottom of the window opening. After that...I can't remember for sure, but it seems like there is another bolt on the front end of the piece you're trying to replace, and maybe even the back too...it might just press on though. Once you get it loose, just work with it to get it out. Putting in the new one is where you'll need to be careful. You have to hold it just right to get it inside the door to avoid twisting or warping the metal in the seal.
Sorry that it's not too thorough. If you need, I can refresh my memory and get back to you. I'd just suggest dedicating 4 hours to learn how to do it yourself. Everything is unbolt/unscrew...no rivets to drill out or anything.