Hi,

You are correct that there’s four fasteners. Two bolts on the back side and two nuts on studs in the front.
You will need to move the seat back and forth some to get access and have the seat balance itself to lift out easily.
The nuts are down in the track and the rear bolts screw into floor bracket with one being covered by the plastic cover with two plastic push in pegs. They pop out fairly easily with a small thin forked tool or even a carefully place putty knife. Push from the inside if possible.

Yes, there can be seat heater wiring on some models that unplug. The 200s did not have seat passenger sensors.
In the very last years of the 240s they did have a steering wheel SRS air bag only. The activation equipment is in floor box cavity beneath the drivers seat.
Here is where you may want to be careful about get that unit wet with any solutions so be kind.

Here is another thing that you are going to run into.
The carpet is completely removable once you have all the seats out but they are in two pieces, front and rear sections.
The rear seat is clipped down really well and the only way to release it is to push the center bottom in hard enough to force a wire rod running along the front lower edge. Do not think you can pull the ends up or you will bend the seat out of wack!

The kicker here is under the carpets, where the foot wells are as they have padding underneath.
It is a combination of flat rubber and foam rubber, of which actually falls apart if not handled with more than kids gloves!

The idea of putting solutions on top of that or into them will certainly cause headaches.
It best to leave them alone if at all possible.
If you suspect spillages and what have you, then the extraction system won’t do a good job either.

I would remove only the carpet and pressure wash them away from the inside of the vehicle.
Survey what you are going to find before shooting juice to the interior.
Many cars have less than outstandingly plush or long wearing carpets so treat the accordingly.

If you are trying to restore a car or rework the floor padding from any excess wetting or flooding, then you have already got a mess.
The flat rubber combination used just crumbles with age and being shaped so long in place.
I don’t know which was worse to put into cars, jute or open cell foam rubber. It’s all cheap garbage. One has to admit cardboard door panels with plastic sheeting that supposedly keep moisture at bay always seemed lacking ingenuity with bean counters snooping about.

Sins are hidden from the consumers eyes!
Plastic engine covers are the most favorite marketing gimmick.
The more expensive the car the more the fasteners are hidden.
Luxury's appears to showcase “eye candy” with us not knowing how things work or being held together.
The 240s were the last of honestly BUILT vehicles to go the years for a family.

To really dry out a car an electric dehumidifier is the best next thing to use. Close it up tight so it warms and extracts.
The next best is baking things in several days of summer heat and a fan.
That is, heat without humidity!
Cutting loose with water and a vacuum extraction sounds good and easy.

Just Be careful!

Phil