Originally Posted by gsxr

You can change the plugs with the manifold in place but it's a nightmare. I'd pull the manifold. No need to remove the injection lines - leave them attached to the injectors and injection pump. Replace ALL SIX plugs... AutoZone has the best price I know of, and they have Bosch Duraterm plugs. Use Bosch or Beru plugs only - not Monark, Autolite, or anything else. While the manifold is off, use the time to clean things up, use a new OE/dealer manifold gasket if possible (this will have a metal reinforced core, most of the OEM/aftemarket gaskets are paper only). Also replace all the metal injection line clips & buffers - see photos below.

As a 1987 300D owner, read this article if you haven't seen it yet:

Originally Posted by gsxr

You can look up the part numbers with the Russian online EPC... they'll be in the engine section of the 124.133, I think under "Intake & Exhaust Manifolds".

http://detali.ru/cat/oem_mb0.asp?TP=1

Pretty sure you just need the long gasket between the intake and head, and the small oval gasket between the crossover pipe and intake.