I just did a seat swap on an 05 base model roadster for slk seats. My car did not have any airbag plugs under either of the factory seats, but the SLK seats did have a yellow 3 pin connector under the passenger seat. Im guessin it has a pressure switch or weight sensor that is connected to the passenger airbags some how. You still want to disconnect the battery however. I just swapped out the seat belt latches to keep the harnesses crossfire style. Now for those seat heaters...