Reading this thread it seems there is an ECU on the steering motor, so if your steering ECU is now no longer the original one, then a proxy alignment will be required (so the two ECU's can communicate signals to each other). The airbag has an ECU too, and I suppose that also doesn't recognise the steering ECU now, so the same thing applies.
For a proxy alignment you need to have the software and leads to connect to the car's diagnostics port. A fiat dealer will have one for sure but some other specialists might have a similar system that can do a proxy alignment on a Stilo. You might need to ask.
If you have a laptop and like poking around with electronics then you can buy the software and the correct lead so that you have it for any other time you need to check the ECU codes or align something.
Ralf S.