I believe you already have your answer from the other thread, but...
When I repainted mine 2 year ago, it just came right out once you remove the bolts holding the auger in place (i.e. both sides of the snow blower housing.) The impeller is pinned to the auger gearbox, but the impeller itself is just splined to the main gearbox in the rear (nothing else holds in in place.)
Maybe it's just rusted in place?
Also, you can get a parts diagram from Cub Cadet if you go to the parts section on their website and type the 190-341-100 part number in. It will pull up an illustrated parts breakdown of the snow blower and all the sub assemblies.