This is something that should and needs to be done with ALL impellers when you are removing them… Once the cover plate is removed, you need to spray WD-40 (or something similar) inside the housing and into the spline or key & shaft area (liberally) and then BUMP the engine. Then spray it one more time and bump the engine again… TWO times and now that impeller is ready to be removed.
Once you do that, it will “break” the dry bond that always seems to occur between the rubber and the housing and also loosen up the spline (or key). This is essential during any impeller removal and now the impeller will slide out EASILY.
When installing a new impeller, throw out all that crap about lubing – Use any common white lithium grease (or similar grease) and life becomes easy for all… Instant prime too. Be sloppy with it, coat all inside, shaft and impeller and I personally guarantee it with not hurt your impeller if you are planning to finish the job and test the engine within a few days or so… That old wives’ tale has got to go – But, if this makes you squeamish, then go ahead and use a synthetic or silicone based grease made specifically for all types of rubber elastomers.
Also, all that crap about which way the vanes have to go is also just that – TOTAL CRAP… It makes ZERO difference as the split second the engine cranks, the blades will flip as needed. But of course, after any impeller replacement, do a test and check for leaks, etc.