OK. I was able to completely remove the rear seats. It's very simple once you know how to access the rear bolts. In the process, I discovered why there are no DIY tutorials on how to change the fuel filter or fuel pump on a W166 (even though there are plenty on W163, W164 and other models). It is because you cannot access the fule filter and fuel pump through ports under the rear seat. You have to drop the tank. To drop the tank, evidently you have to remove at least part of the exhaust system and the driveshaft. This job was above my capabilities so the vehicle is at my local dealer for repair as I type this.
Anyway, in addition to the .pdf's provided by ytech15 (thank you again), here are some pics to explain the process. I marked bolts with yellow masking tape becasue I am not good at adding arrows with photo editing applications:
Here are the three bolts you need to remove on the 60 (driver's side)seat:
To access the rear seat bolts, you need to remove the cargo hold downs directly behind the seats:
Then you can gently pry off the trim panel behind the rear seats:
This will allow you access to one bolt on the driver's side:
...and the bolts for both seats in the middle:
Note: You are going to have to also disconnect the airbag connector on each seat. The WIS instructions advise to disconnect the battery before starting this procedure. I did not. Even thought I did not start the engine with these airbag connectors disconnected, I did receive rear airbag malfunction messages after buttoning everything back up and starting the engine. I asked my service adviser to reset these while they are working on the vehicle.
The seat cushion parts of the seats are dead simple to remove. Flip them up and you'll be looking at all the bolts you need to remove.
In order to peel back the carpet to access anything under the seat, you need to remove the door pillar trim on each side:
And once you peel back the carpet, you will see a lot of stuff. But NO FRIGGIN' FUEL PUMP/FILTER ACCESS PORTS!
