Cab Rot Around Rear View mirror at Windshield

[jlampka]

Hi All! I have a 1971 Chevy C20. Just wondering if this is a major headache to replace my windshield and weather stripping since the windshield is cracked. I have some rusted areas on the inside where the rear view mirror is located ( see photos). This seems like a common problem - any/all advice on what I'm in for appreciated.

Without tearing into it, I don't know if it effects the windshield weather stripping or not.