Corby,

On the 240D there are two sets of assemblies with intake and exhaust valve rocker arms set to match the pattern in the head. In the 300D I imagine since I have never seen one, the five cylinders make this operation two sets, but one has two the other three cylinders worth of rocker arms. Yes, you do the ones that you will be working on first, then replace them and go to the next set, or you can take them all out (one set first, then reposition and do the next set) and then work on the valves one set/seal at a time.

The need to keep the assemblies match marked to the location they came from is still just as important, or maybe more so, as they will likely fit in the wrong position, but not turn out ok in the detailed geometry of the valve actuation. Hope this helps,

Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)