AquaVac 2.0 pool cleaners - impeller blade replacement

I have an old model AquaVac 2.0 pool cleaner that needs the impeller blade replaced. Sounds pretty simple but I am stumped on just how to get the old impeller blade off. I have removed the top screw holding it in but the plastic shaft of the impeller won't come off. There appears to be a metal cylinder and flange that the impeller shaft sits in but when I attempt to loosen the flange I get nowhere. I cannot locate any replacement manuals for impeller blades for this model and do not know where to go from here.
Replacing an impeller would seem to be not a big deal but this one has me stumped.
Any words of wisdom?
I really could use some good advice on this before I just give up and go buy a new pool vac.
Many thanks.

~Brian in GA