2000benz

I own a 2000 C230 Kompressor and my wiper initially got stuck on intermitant. Took it to dealer and they said it was the wiper relay which I ordered and replaced. Now don't work at all. Dealer did dianostic and said it was a module that need to be replaced that would cost me $650 which includes my dianostic charge. Does any know what module they are talking about and how to replace it?
Thanks