living in az they line all the sides of the highway with small rocks. The rocks get on the road, they get kicked up and because of it you get glass insurance and your lucky to go 2 years with out getting a new one. Because of this my seal never dried out but it happens and should not be a huge deal to get replaced.
I think the seal should be able to be replaced with out the glass but I am not a glass expert. I am pretty sure it is the first part to come off in the glass removal process and the last part to go back on. While it does seal I think the stuff they put under it that it covers is what really seals the glass to the car.