Properly lubed steel gears will not wear each other out in several life times. That is my biggest hate for plastic, the only reason for using it over steel gears is cost. The plastic gears are cheaper to make.
Cari,
I've got a couple machines with cracked gears like that and I've pretty much side lined them until I can find a new gear.
As far as I am concerned it's much better to replace the old gear before it frags inside the machine than after.
Sorry to see that, really I am.
Joe