I left my wipers "up" over night, and had 4 inches of snow on the car in the morning. When I turned the key on, the wipers came down, but got jammed in the snow build up. I've replaced the wiper motor (twice, with the same results) and now, the intermittent wipers do the pause at the top of the travel rather than down and out of the way. Also, when I turn them off, they won't go down the final bit...they won't "park". A tranny mechanic (another story) said it was most likely the park module for the wipers. Is there such a thing, and if so, where the heck is it?

I believe the park module referred to is the wiper circuit board that is part of the wiper motor assembly but you've changed that twice. It sounds more like possible mechanical damage to the transmission part due to the weight of the snow or there is a metal tab located at the wiper arm base and motor that could get bent out of shape causing a similar problem. The tab is supposed to be at a 90 degree angle. On the latter, the typical symptoms is the wipers stay straight up and do not park when turned off.