I ordered 2, 8, 4, and 10 from the water pump fiche, and replaced all of the O-rings/seals on the crankcase cover as well. I figured it was good practice to replace all of them (and I think the manual calls this out as well).
I'm not sure how to get the water pump out of the crankcase cover without the special tools. The impeller is pressed onto the shaft on the outside of the case, and the drive gear is pressed onto the shaft on the inside of the case. Parts 2, 8, and 10 are all pressed into the case cover.
I think I just used Permatex grey on the case cover when I put it all back together, but it could've been the Hondabond stuff. Not sure anymore, and it probably wouldn't make a difference.
2008 Ducati Monster S2R1000 (the mod whore)
2003 RC51 (sold)
2002 ZX-7R (sold)