Steel nuts will never decay, so this fix will last the life of the motor.
Note that it is NOT necessary to fill the housing with grease, so don't. A light film on the shaft, plastic gear teeth, & metal gear O-ring will be enough.
Original Delrin pins are available, but they'll break down eventually. See p.35 of this PDF:
https://www.henrysautomotivewarehouse.com/2017_web.pdf 
