Yea i got some personal experience with that, couple days ago I looked at the back window and there was water drops just hanging there, inside.
Water was dripping on the backseat from the window seal, so i took it too a glass repair shop and the problem they were very familiar with.
They said 85 bucks replacement of the seal.. if it's the butyl seal. Now these 1997-2003 trucks have a common problem with the back window frame cracking and if its that, then it will be a 400$ replacement of the whole back window so i was praying that it wasn't the frame and it wasn't, luckily. And just fyi you can't get the stock mirror finish windows, or at least that's what they told me.
And btw- no need to remove the backseat back rest
... they did it by just pulling the fabric back and revealing the nuts.. hope this helps some jb451