Actually, its very common to leak from the rear passenger side of the head gasket, so unfortunately that is incorrect information. It widely occurs on many M103.
Get the head skimmed, pressure tested, new valve guides and seals. Done this job 3x so far on two M103's.

Don't remove the intake manifold, remove the bolts and push it towards drivers fender. Its far more hours and risk touching old electrical wires and removing the entire fuel injection side.

My biggest recommendation is do NOT use ANY other head gasket other than Genuine MB. I used Victor Reinz, and ended up having to re-do it again after 20k miles. They are not the same quality. Factory head gasket is only $50, so there is no reason at all not to use it.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k