How to know what pump impeller

My pool pump motor is dead, and the shaft will not turn.  It is the A.O. Smith 1 H.P. Square Flange Up Rate Motor - USQ1102.  I see that it is available.  My problem is that I cannot get the impeller off of the shaft.  I am afraid that I will destroy the impeller if I apply any more force.  Before I do that, I want to be sure that the impeller is replace able.  I have not found a number on the impeller.  The diffuser is C1-200PA which seems to be Pentair.  The tag on the case is damaged, but it seems to be A5E-124L.  In case I damage the impeller, what do I need to replace it?

Hello - yes, the impeller for your Sta-Rite Dura Glas is replaceable; part number is the C105-138PEB.

Did you get a replacement shaft seal to complete the installation of the new motor? Going by the -124L suffix of your model number you have a pre-98 model, which key eight on the parts diagram.