Easy as hell to change... pull the trim around the window. I just replaced the seal around my window, it was leaking... 3 bolts top and bottom, and one on either side, than just push around the edges and it should pop out.
Don't feel bad, I busted the sliding read glass in my 2002 Edge by trying to get into my truck with a flathead screwdriver after I locked my keys inside for the 50th time. I unlocked it 49 times with the screwdriver before, but I guess I applied too much pressure this time ...lol
I was able to find a rear slider at a slavage yard pretty easy. I think I saved around $125 by getting a used one.