Back window leak

I know this is a little off topic. My wife's 99 reg cab f150 has a sliding back glass that leaks. I have looked on other forums but haven't found one with as much intellect as this one.


I am looking for some kind of breakdown of the seals, looks like it has two of them. The window and this generic looking plastic ring around it about 1 1/2" wide. Any help would be great so I don't break it.