Hi Andy
From memory the Airbag control unit is mounted centrally under the top of the dash just above the heater. You will see it once the main dash is removed, careful with your windscreen. With the battery disconnected you can remove the unit and then the airbags. and then the light when it shows. There is no problem with the car starting after that.
I don't think your door panels will fit as the Mk2 doors are a different shape, you may be able to "unwrap" the panels, trim and "re-wrap" if you see what I mean. The seats and other bits should be a straight swap.
Your kit is being collected on Monday