Looking at this picture from the GMB page I know how I would remove it, hopefully w/o damaging the bearings and seals.
I would use an inductive heater to heat the impeller's hub and then use a puller to remove the impeller. I've had some impressive wins and a few catastrophic fails with this technique at work.
Seriously, if you've got the spare change then buy one of the chinesium inductive heaters off the jungle and try it out on various things. Some things it works dramatically better than anything else you've ever tried, and some projects are duds.
It may also be possible that they're buying them less the