I wouldn't worry about changing the sparkplug wires unless they are badly damaged or show too much resistance.MB uses some darn good wires, the wires on my 4.5 appear to be original (still have the cylinder #'s on them), are about 30 years old and look like crap, but resistance is correct and there is no arcing.
Your noise that was diagnosed as the cam, could also be the belt tensioner going south. Does is sound like a rattle?
'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.