124 windsheild wiper motor / arm problems

[300celvr]

Hope some body has some experience with this. I have a 1990 300ce. Last monday while driving in the snow, the front wiper arm became herky / jerky. Started stuttering and then finally stopped, blown fuse. Replaced fuse and was good for another jerky sweep or two and then blew fuse. Went through 6 fuses to get another 5-6 miles then another two hours with out a wiper in a snow storm. Is it the motor or the wiper arm transmission. Where do I find a diagram on removing and replacing this assembly and possible a reman. or good used working part. I am afraid to ask the dealership how much for both new pieces. Any help would be greatly appreciated. thanks in advance!
Greg