The heater on my Renault Megane Cab is not blowing air?

I have an 04 Renault Megane 1.9 DCI Cab. Today when I started up the car the blower didnt start. The garage says the motor has probably blown with the cold weather and then the thaw causing water to drip into it. They say it's a big job to fix and just wondered if anyone has had this problem and how much I am looking at paying