Where will you be staying with the C in the Toronto area. That way you could get directions on public transportation. If you can come in on the subway/Go Train/Go Bus it is an easy walk from the main Union Station to the Hockey Hall of Fame.
There are some above ground parking lots, just south of the Sky Dome on Queen's Quay (I have seen C motorhomes parked there before). But as others have said try to avoid driving to Toronto. You could also check out Ontario Place parking on Lakeshore just west of Skydome. Ontario Place is closed but I think parking is still open. Lots of room there and then cab to where you want to go.