Thanks Dux,
After posting my question , I went back and looked, scratched my head, and re-read the DIY article by Brotherton and then....EUREKA!...his mentioning of the upper guide rail pin registered. The MB WIS confirmed removal of this by the diagram although no instructions. Used your home-grown certified MB shop tool to remove it and voila! the cover came right off.

A stretched chain explains the 5 deg cam timing retard to my satisfaction and I will put in a new chain and tensioner.

Again, thanks for your help,
JOhn