Here is a short discription how to swap the side-airbags and seat belt tensioners...
seat belt tensioners:
1.) remove the "L" connector from the yellow seat connector
2.) remove any zip tie and clips etc. from the seat belt tensioners cable
3.) loose the torx-screw at the tensioner (believe it was a T50 - but not sure)
4.) remove the cable and tensioner ... remember how it was fastened
5.) swap the tensioner to your new seats
6.) connect everything like it was before
7.) done
side airbags:
1.) remove the bezel on the back of the seat:
1.1.) there are 2 clips on the bottom of the bezel. You have to cut them with a carpet cutter or something similar. You will need new ones: part number: 52 20 1 964 201
1.2.) after that you have to twist the bezel a little bit clockwise und push it downward. Be carefull, otherwise the mounting parts could brake!
2.) take the bezel aside
3.) remove the seat cover on the side where the airbag is situated. You have to remove it from the seat frame by pushing it inward the seat.
4.) it should look like that:
the black box is the airbag!
5.) remove the 2 screw nuts with which the airbag is attached to the seat frame. Remember how many turns it takes until the screw nut comes off.
6.) remove the airbag connector from the yellow seat connector
7.) remove any zip tie and clips etc. from the airbag cable
8.) put the airbag with the cable aside ... remember how it was fastened
9.) swap the airbag to your new seats
10.) connect everything like it was before
11.) done