I'm having a hard time getting the passenger side seat removed on my '89 300CE. So far I've managed to remove the plastic cover on the left side but the one on the right is proving to be rather difficult. Is there a special way to remove the plastic trim that covers the 10mm bolt? I really don't want to risk breaking it off.

I'm having trouble by your discription.

There is 4 bolts that hold the seat down, one which holds the seat belt to the tunnel.
You take the cover off the seat motors, remove the electrical connection. take the 2 bolts off the front, and rear- might have to move the seat so do these before the electrical connnector is removed.
The back screw you pop the black plastic cover off the screw. All 5 are 10mm heads.

from memory!
M

On the coupe models there is very little access to the bolts without removing the plastic trim. I did eventually manage to get the covers off without breaking them off.