Replacing chopper

I can't find much info on this model because it's so old; I need to replace the chopper (actually, install the chopper - all that's left is the retaining spring). It's in a very difficult place to reach, and I'd appreciate if someone could either point me to the service manual or walk me through it (all I can find is the owner's manual).
As best I can tell, the replacement kit is:

PART NUMBER: WD19X60
Substitution: WD19X10032


Thanks much!!