I happened upon a wrecking yard W210 with sheepskins on the front seats. As expected, the seat surfaces were dull but with no sign of wear. Rather than fit complete seats of unknown age and function to my car with seats that work, I removed the upholstery (and attached padding) to transfer to my car. Here's how *I* replaced seat back upholstery. I'll document the seat bottom process later.
Tools: T-20 Torx driver, flat blade screwdriver (to pry), hammer, possibly an awl or ice pick (cue Bernard Herrmann score)
Time: once I figured out how to remove the upholstery, it took me 10 minutes to remove and 10 minutes to install working methodically and checking my work.
Remove two screws from along the bottom of the rear cover using a T-20 driver.
Pull the rear cover down and away from the seat. Set aside.
Use a flat blade screwdriver to spread the fingers of the socket holding the end of the head rest posts to the riser mechanism. Pull up firmly on the post to release from the socket. Repeat for the other post. It appears that you can just jerk the headrest posts out of the sockets but I didn't want to chance damage. Lower and/or recline the seat as necessary to remove the head rest.
The upper hem of the upholstery tucks into a notch along the upper rear edge of the seat back frame. A screwdriver tip is in the notch in this picture taken from ahead of the seat.
Pull the hem forward and free of the notch starting at the corners. The head rest riser gets in the way towards the middle but there's enough room to remove the hem. I would have tried something like an awl or ice pick if necessary but my fingers were strong enough.
Reach under the upholstery just released and feel for the tab holding the head rest guide to the seat frame. Press the tab towards the front of the car while lifting the guide. Pull the guide free of the seat. Repeat with the other guide. It's possible that a quarter counterclockwise turn of the guide as viewed from above would free the guide. I forgot to check with the upholstery off.
There are 5 hooks along the bottom holding the lower hem in place. It might be possible to simply unhook the upholstery but I bent the hooks outward to make it easier. I found it easier to first unhook the leather then the backing material.
The side hems have a plastic strip that hooks to vertical posts in the seat back frame. Pull the plastic strips toward the seat centerline to release them from the frame. I pushed the slots in the plastic strips with a flat blade screwdriver. Repeat for three attachment spans on each plastic stirp.
There are 2 more hooks just above and outboard of the hooks above. Bend those hooks ouward as well. Then unhook the lowest plastic strip slot.
Take the lower ends of the side bolsters and curl them toward the centerline of the seat to unhook them from the seat back frame. Pull the bolsters forward as they release. Mind that the upholstery pad lower section has a flap that hooks to a metal rod along the bottom of the seat back frame, and the lower hem released from the five hooks have to come through the break between the seat back and seat bottom. Pull the upholstery up and away from the seat back frame.
Installation is the reverse. Set the replacement upholstery firmly on the upper part of the seat back frame. Work the side bolsters onto the corresponding edges of the seat back frame. Working through the seat back frame coil, hook the flap on the lower edge of the padding on the same metal rod along the bottom of the seat back frame. Send the lower hem through the break between the seat back and seat bottom. I found it easier to first hook the white backing material then the leather hem. Clip the plastic strips along the side hem onto the vertical frame members and lower end hooks. Tap the hooks back as they were. Feed the upper hem into the notch along the upper end of the seat back frame. Press the head rest guides into place noting the orientation of the retaining tabs. The lower end of the guides fit into corresponding holes in the seat back frame. I used my finger to align the guides with these holes. Tuck the upper hem into the notch along the upper seat back frame. Fit the head rests ensuring the post ends properly engage the sockets in the riser mechanism. Poke new holes in the lower hem for the rear cover screws. Slip the upper tabs of the rear cover under the upper hem area then position the rear cover so the screws can be tightened.
98 E320s sedan and wagon