Just to follow up, the wiper now works great. I'd forgotten what an impressive piece of engineering it is. The gear is still cracked in half, but it's been that way for the 15 years I've owned it so maybe it will outlive me.

I just took my time and carefully cleaned and lubed everything with WD40 to loosen it up and a synthetic red grease or ATF for lubrication. The daily drivers sit outside and we have a lot of trees that drop all sorts of crap in the spring. I couldn't believe how much crap had gotten into everything. It was packed between the wiper transmission and the windshield.

Anyway I also replaced the blade with the best one I could find and it works perfect. Absolutely smooth and silent

So don't panic if your wiper slows down or starts to stick at the top of the travel. A careful cleaning and lubing may be all that's needed!