I presume when you say you want to remove the "wheel", you mean you want to disassemble the impeller, shaft and hub from the pump body. I bought a 1.9 CIH water pump repair kit off ebay (yes, I DO buy a lot of Opel stuff off eBay!) a while back to see if I could rebuild a worn out Opel water pump. I had heard that water pumps were re-buildable, but I had never tried one myself. The kit came with a new impeller, a new shaft, a new bearing and a new mechanical seal. About the only thing that needed to be re-used was the hub and the body. So, it looked like I just had to disassemble the pump and install the new components. Well, easier said than done!
I first tried to press the hub off the shaft, using my 12 ton hydraulic bearing press. No luck, but mainly because it was hard to fit a bearing splitter between the impeller and the housing. So I tried to press the hub off the shaft, also using my bearing press. Also no luck. So I tried heating the hub, and then the impeller, and pressing them off when heated. STILL no luck! And when I REALLY heated the impeller and tried to press it off, it broke, along with the pump housing.
After examining the broken parts, I could see that the hub and impeller were indeed pressed on to the shaft, and so it SHOULD have been possible to press them off. But I doubt that no matter how you tried, you could press then off and then re-use the parts.
And just so you know what else NOT to try, I also tried glass bead blasting an old pump to see if I could clean it up. But even after packing rags around the shaft, impeller and into the pump inlet, the glass bead got into the bearing, and the pump was ruined. Well, this pump was already worn out, but you could clearly hear the grit in the bearing.
My advice? Clean the pump as well as possible using solvent and then brake cleaner. If you still want it shinier, you could try aluminum engine paint (it works QUITE well, if you use the high temp manifold paint). Or just buy a new pump from OGTS (or your local auto parts store), and it will be fairly shiny already, and that much more reliable. Not polished, but you could also try that too. But THAT is a whole other thread!
Anyone done aluminum polishing (valve cover, intake manifold, timing chain case, water pump) that they would like to post some photos of the process and the tools needed? If so, start a new thread, or add it here and I will split it off to a new thread.