Thanks for all the suggestions. I'm going to try the hand-turning of the shaft tonight, make sure that works as expected. I'm also sending the propeller off for repair to the shop the dealer uses.

I guess my only remaining fear is that if I find that that the shaft turns as expected (easily and evenly), and also if after the prop repair, the boat doesn't vibrate anymore - is there any reason to fear that anything else is out of whack that I'm not noticing? In other words, can I save the money I would otherwise spend having the dealer inspect it?

Thanks again guys!