I've just looked at eLearn, the Fiat genuine instructions. I don't think they are much help.
Those instructions say the fascia support beam needs to be removed, before the control unit (The whole control unit is one piece, including teh ECU built into it.), but the instructions for the support beam, suggest the controls come out before the beam.
The beam requires removal of one front door.
Have search through the forums, use the advanced search facility. I'm sure there are other threads, and I think one about replacing those controls. Should be remove the outer panel, then the screws that hold the unit in.