Re: re-fit of 156 interior
I did mine, no problem with the airbags or the warning light.
Assuming that both old and new seats have airbags, simply disconnect the battery AND WAIT 30 MINS for any residual capacitance charge to discharge before you disconnect the old seat wiring connectors.
Unscrew the old seats, screw the new ones in, reconnect the seat wiring and reconnect the battery.
If you wait the 30 mins, as suggested, you should have no problem with the airbag light coming on or needing resetting.
As above, the main hassle is the door cards (and I had to actually swap the leather inserts over on mine because the leather doorcards were the older "shiny" type of plastic moulding not the newer "mark 2" dull tactile plastic.....), so I actually had t separate the leather mouldings and fit them to my own doorcards (used Evostick contact adhesive and duct tape to fit them back onto the doorcard)
2004 Silver Audi A3 2.0 TDi S-Line DSG (eBay!)
OEM Xenons (retro-fitted), PIAA silicone wipers, integrated Parrott CK3000 bluetooth phone kit, O2 XDA2 PDA/phone with TomTom wired GPS
Ex - 1999 156 1.8TS SP1 (1999-2003) + 2002 156 2.0JTS Turismo (2004-2006) (fell off Snake Pass backwards at 60mph...)