Has anybody ever replaced the full heater on a fabia 2010

When you say full heater, what do you mean, the whole heater assy ? or matrix etc ?

 

Is this because of a fault you currently have or are you looking at a retrofit ?

Because the flaps are not working and I don't know if its the motors or the flaps 

The flap motors tend to be remote from the heater, so if any of them have failed, then either exercising them(if you are lucky) or replacing failed ones is what you need to do.