[greglepore]

I have a '96. The engine itself is dead nuts reliable. The pre 96 cars, though, have some things to be aware of-the well known wiring issues. The main harnesses hopefully have been done (look for receipts or delphi tags). But even if they are, a couple things lurk-the throttle body actuator wiring degrades; also, all 600s had ads, and i can tell you from experience that even the later cars have early ads harnesses, and they crumble, as does the wiring at the valve body. It can all be redone, but is tedious. The shocks are reliable, but the spheres are a maintenance item every 60-80k. Mine was converted to standard suspension after spending $$$ trying to sort it.
All 600's eat motor mounts and trans mounts-not a major issue but something to be aware of.
If the valve cover gasket is seeping, keep in mind that the manifold has to come off, along with all of the injectors and their wiring. Also, deep in the v is coax for the knock sensors, don't disturb it if possible as the insulation cracks and the coax is nla.
The top cyls will need to be done at some point if they haven't. Top Hydraulics, under 1k exchange for parts, but its 15 hrs diy.
I had a 95 e320 previously. My 600, apart from the top stuff and the ads, has been mechanically as sound, but its a 96. Other things that changed are the mafs and engine management, the later mafs are avail from china for 40 bucks and work, the earlier ones not. The 94 still has 2 distributors and plug wires, the later are c.o.p.
Radiators have plastic end caps on all, but there are full alu replacements available.
The biggest problem with these 90's MB's is that MB is not the company it once was in terms of parts support, discontinuing stuff that they used to carry forever. While there are some parts available in the aftermarket, not all.
If you want to do a deep dive, feel free to pm me and I'll shoot you a phone #