but I did manage two sparking plug changes on my S-Class 320 ( same engine) with judicious and careful use of a normal open ended spanner, and a pair of long-nosed pliers and a long nosed mole-grip for the tricky ones. Most came off with a bit of a jiggle without resorting to tools. It depends on luck I suppose.
It looks like a nice tool, but I won't be getting one unless my 'gorilla' technique completely fails me.( he said, tempting fate this early in the new year)>