Advising that a spinning glow plug is grounds for replacing the head makes me question their renown. If the head has to come off, might as well fix it. Have the valve guides checked. While everything's apart, consider whether you want to keep EGR active. State inspection requirements might trump your conscience. If you decide to disable EGR, this takes some research rather than just a capping a vacuum line, have the manifold and related airways cleaned.

Corona's Auto Parts in Hartford, CT has a head off a 99 E300. Check car-part.com .

Sixto
87 300D