Many thanks to JFSEHL for the tip about wiggling the seat cable to see if it would temporarily enagage enough to move the stuck seat forward to gain access to the rear bolts., IT WORKED !!
I was able to repair my non adjusting driver side seat... it was bad cable.. the cable end was rounded off.
Being a rookie at this somethimes you stumble across stuff that might be useful while going about things different than a more experienced person with MB's.
If my problem had been due to a bad motor rather than a slipping cable, I discovered a way to manually spin the motor to move the seat, when I took more stuff apart than what I needed to while swapping out the bad cable.
If you remove the plastic side trim from the lower seat by gently pulling it towards you to disenage the plastic "hook", you will gain access to the seat frame.
The seat motors are bolted to this side frame and the motors have the same square slot on the back at they do in the front where the cables are. There are holes in the seat frame that line up with these slots.
I experimented with an old cable and found that If I pulled the cable out of it's sheath, I could fish the cable end through the hole and into that slot and then manually move the seat by turning the cable slowly with a cordless drill.
Anyway, this may be "old hat" to you veterans, but I thought I'd pass it along anyway as it was kinda neat to discover it.