Hi

I am new to Mercedes-Benz and diesel cars for that matter.
I just purchased a1983 240D. Its in pretty good shape but the rear window seal is baddely cracked. Their is no visible rust around the outside of the rear window but their are some rust/water stains on the rear of the headliner. When i gently poke at the headliner I can feel crunchy stuff for lack of a better term.
I have read horror stories about the seal channel deteriorating to nothing. If the channel is bad is their any way of telling without pulling everything out? All I really need is some words of encouragement.

Thanks