Hi mate,
Ideally you would take the electrical seat loom with the seats from the donor car and then retrofit it to yours.
then connect it back to the fusebox and plug it into your seats,airbag wise i was lucky that when the breakers removed the seats, they cut the loom leaving me both plugs, i used Elsawin software to identify the wiring and match the new plugs to the old wiring.
Are your seats heated as well? if so you would need the 2 dash switches and additional loom.
I have a recaro plug pin out for the S3 somewhere, ill try and find it, if you plan to make your own loom.
Hope this makes some sense to you?
One other note: my old seats were held in via torx screws, the facelift are held in with nuts.
Steve