1998 Isuzu Rodeo Question Water Leak

Interior problem
1998 Isuzu Rodeo Question 4 cyl Two Wheel Drive Manual

Sorry, I selected "Interior" as a category due to a more accurate one not being available.
I have extreme water leakage into the interior of the vehicle from the windshield (from rain & can't take thru a carwash).
What I would call a "gasket" along the top of the windshield shows wear and there's some rust along where the metal meets the windshield.
Do I have to have the "gasket" professionally replaced? Or, can it be removed & replaced with a "self-leveling" 3m type gasket making product? Or, can it be left in place and siliconed over to seal the leak?
Thanks