The labor guide gives the time for removing with intake removed. I have never replaced a plug wire on a Mercedes that wasn't over ten years old. The only problems they ever have is the resistor end at the plug. A good engine analyzer will easily pick out bad ends and they are easy to replace one at a time.
The only time I replace the wire is if it gets burned or it petrifies and cracks exposing the copper core. The key is the COPPER core. The voltage has no desire to leave the wire.
If I did remove the intake I would use whatever MB gave me for gaskets. They have had some intake seal problems and the best material is likely to be whatever MB is using at the moment.
BTW the spark plug resister is MB # 000 156 66 10 and lists for $44 but you should be able to get it for much less.