Prepping and painting the narrow trim piece may be easier than you think. If you're careful, you should be able to remove (and reuse) the rubber seal. With that out of the way you could mask both sides of the trim so you would be able to sand and paint it without risk of damaging the rubber bit, the windshield or the paint.
I was able to replace the trim on my car so I guess that's proof that it can be done but frankly I don't recommend it...
cheers - dj
dennisjones.tripod.com