Well,
I yanked the seats this morning. Everything went pretty smooth once I figured out how to access the bolts since the seats were stuck in position (battery and cables gone). Took about 45 minutes to yank both.
Got home and started separating the seat back from the cushion and in the process learned the secret to undoing those reusable zip ties, what a snap with offset needlenose

. Before skinning out the replacement seats, I pulled the passenger side from the 560 and started careful disection of the cushion. Sure enough, the heater elements are sewn in just as Mark stated.
Actually, there are more acurately, sandwiched in between the leather and a piece of heavy muslin. Don't know yet if the pleat pads on the nonheated seat are separate strips or not, but on the heated seat the element has a "finger" for each pleat, with individual pads. everything is then covered by a piece of musling and sewn down the fold between the pleats.
Now I'm off to the fabric shop. Gonna try to find some heavy muslin, heavy thread and a heavy needle. We'll see how my sewing skills turn out. Good thing I have a long weekend, but I don't think it will be enough time

.
After I get the hang of this, or one seat done, I'll try to get a few before, during and after shots.
__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.