"William,
I am not sure why
"William,
I am not sure why you are concerned with getting the impeller and shaft out of the pump at this point if the pump is still on the engine. According to my best recollection, you can't get at the seals that need attention without removing the pump from the engine. When the pump is removed from the engine you can push out the shaft and impeller from the back side then the seals can be removed and replaced (again from the back side). I know you said the bolts holding the pump on to the engine are rusted but sooner or later you are going to need to address it and now is better then when you are in a pickle. Just be patient and you will get it. Soak the bolts with a good agent like liquid wrench, WD-40 and let it sit for a day. Try tapping on the head of the bolt or heat the bolt heads and then spray with an agent. If you go the "gorilla" route you are likely to get an undesired result e.g. bolt head broken off.
At any rate below is what the manual says for removing the impeller & shaft from the front side, uploaded pic for you as well.
Remove the cover. Watch out for water pouring
through the pump. With the aid to two
screwdrivers prise the shaft with the impeller out of the housing sufficiently for the screw which holds the impeller to be undone. NOTE! Lay
some kind of protection under the screwdrivers
so that the housing is not damaged.
59. Take the screw out and pull the impeller off the shaft. Clean the housing internally and check
that the carrier (MD17) is free from defects and
fit the new impeller. Fit the cover together with a new gasket.
Maybe Vic S. will confirm.
Best of Luck with it.
pic of impeller removal