Regarding the wear ring, I've heard mixed things about aftermarket wear rings. Once I bought one from SBT that was not round on the inside diameter. Had to take a bunch of pics and send it back. After I proved to them that it was indeed defective, they refunded me. If it's only a difference of like $10, I'd go OEM. Otherwise, I'd go with WSM, or whoever makes those rubber coated rings. I've used those white plastic rings before and they seem to work okay, but when I put them in, I always wonder if the fit wouldn't be tighter with an OEM ring.
The best way to get them into the pump: put them in the freezer. This shrinks them down and they slide right in. No pounding, no struggle.