Upper Antenna Seal: How to Affix?
 

Upper antenna seal is completely disintegrated so I'm getting a new one. Do I affix it with some sort of adhesive or does it simply fit snugly over the lower seal?

Are you talking about the seal between the antenna and the quarter panel?

On my w123, removed the housing and the new seal popped into place, then the antenna assemble back in place.

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AFAIK, there is only 1 rubber seal. This one? Soak it in hot water first and it will go in much easier.

If it's the one on top of the 1/4 panel that covers the hole and the base of the antenna, ... pull the old one off, the new one will slip over. You will not need any tools.
I do remember it being a little tricky to get the lower/inner ridge to seat all of the way down, a little twisting and wiggling (the seal, not the wife) will make it happen.

On mine there are two: upper and lower seal. The lower one is cylindrical and goes down the hole around mast. The upper one fits over the lower...it's sort of "beveled" so it deflects water away. That's the one that disintegrated.

Thanks....the twisting/wiggling advice did the trick.