It's not really very difficult at all.

How To

That's a very old article, and there are a few differences about how I do it these days. Do not use RTV as a sealant, use NAPA windshield sealer. The rubber seal goes on the glass dry, the glass and seal goes on the car dry, and then you squeeze the NAPA stuff btween both surfaces. One tube is more than enough.

Some people has an easier time putting the bright trim on the seal before the windshield goes on the car. I've been able to do it after the fact, but that's the only tricky part.