New head bolts are not always necessary, but I would replace them. And yes, I would send the head into the machine shop to get the guides done. You may never have the head off again - now is the time to do it.

One other dilemma you will have is deciding whether to leave the intake manifold attached or to disconnect it first. Leaving it attached is way easier, but you will need a hoist to remove the head (it's pretty heavy with the manifold attached). If you disconnect the manifold, the head is light enough to lift yourself. Do a search - there is plenty of info here.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280