Welcome Brock to the weird & wacky world of Alfa.
Unfortunately to replace the water pump you must remove the Cam Belt. What's the reason for wanting to replace the pump?
If you're worried about the plastic impeller issue, check the cars maintenance history and see if it notes when/where the Cam Belt was replaced. If it was replaced by an Alfa specialist they would have known to use a pump with metal impeller so you should be good.
Baz