Its hard as heck. You have to pretty much destroy everything about the old one and get all new. AFter that, it doesn't seem to be hard. I have tried a few times to remove stock windows in junkyards without damaging anything...but there is no way around that edging.
but even if you don't use it, why bother going through the hastle of replacing it? It's not like it's an inconvienience having it there is it? I'd be afraid of replacing it and having a leak later or soemthing.