No harm at all except your dirty underwear I believe. Mercedes engines are basically built to rev pretty good. Five thousand is is not enought to disenigrate them really when previously warmed up. Also remember in your instance you were probably still only up against the injection pump govenor. The loss of the injection pump itself is more likely at higher reves. That is the primary reason for the rpm limiter or govenor in these designs rather than the engine itself I believe. Now when you are running away on base oil for instance there is no govenor protection at all. I have no ideal how high the engine can scream as the only fuel limitation then is what it can get. A small amount of medium locktight might be a good ideal on bolts you do not want to torque down too much..