Exchange of heating element

[fantasia]

I have a leak from the heater element in my Octy 2.0 99'

So went on to dismantling the dash then when I got to think that it has Aircon with manual control and there must be placed a cooling element inside the complete heater unit and it must then be emptied for the cooling fluid.

Or is there any other easy way to get the heater element out of the car?