Looks like GPs number 1,3, 4 are all bad.

The intake manifold ends up being fairly painless to remove on the NA version, not sure about the turbo.

3 simple rules have had successful results in changing w210 glow plugs
1) Warm engine
2) Lots of PB Blaster
3) Use a torque wrench to remove and don't go over 50 Nm

If the plugs don't budge at 50Nm, spray with more PB Blaster, walk away, enjoy a beverage for 30 or 60 mintues and go back and try again. Repeat as needed, but be careful on how many beverages you have.

I buy my GPs online.

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Mark in MA
05 MB E320CDI 402k Granite Grey Metallic
05 MB E320CDI 267k Black
05 MB E320CDI 232k White
05 MB E320CDI 209k Tectite Grey
99 Dodge 2500 Cummins 5sp 148k
62 Jeep CJ-6 120k