I am in the process of changing a stator and regulator/rectifier on a 2002 Grasshopper 618. Information and personal experience on these mowers are limited. It appears you have to take driveshaft from engine to gear box off in order to replace stator. It is a Kohler Command CH18 engine, no other details because all identifiable information on engine is gone. This is a customer unit.
The reg/rect is on bottom right side by fuel tank. Never been a fan of Grasshoppers, this only confirms it.