Chiming in for some tips concerning the intermediate levers.
They are not hard to replace, if one has the AGA valve stem tool.
However, if changing the intermediate levers, I would suggest to change out the "roller drag lever" associated with them as well. The TIS is very specific concerning the p/n for those, even they seem the same, they are not. They have the last digit of the p/n different and corresponds to that tolerance for that specific cylinder. They are matched with the drag rollers, which have also a different end number.
If one changes the intermediate lever, but keeps in place the old drag roller, there will be a different tolerance which could screw up the opening/closing of the hydraulic lifters.

Bottom line, when ordering the parts, make 100% sure you mark them for each cylinder (they are 2/cylinder: a pair for the intake - the exhaust have only the drag rollers 2 /cylinder also marked for tolerance). Then take the whole p/n stamped on these parts together with a suffix if stamped. These parts will be ordered directly from Germany AFAIK, and they are not readily stocked at the dealers due to the different tolerances of these parts.

0.02

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Stable: e92is, e46 M54B25, e83 N52, e53 N62 - sold, e39 M54B30 R.I.P.