I took the advice of others here,
almost. The word being MBz started going cheap around 1996. I looked at a lot of the 90's S models (W140 S320, 420 & 500's) and could certainly see what they mean. MBz started taking out a lot of cool little features. to cut costs. (I ended up with a 1997 anyway) For a data point, the model replacing the W140, in 2000, weighed ~800lbs less. (not from a a switch to CF
) Though I vaguely remember hearing they used more alloys on the engine.
I can tell you that the 90's 500's can have some seriously high milage and still run great. ( I looked at one w/ 273K, just for a data point)
In reviewing various repair histories, i saw no big gotchas.
The market on used Mercedes is hyper-soft. Apparently because people do just what you have done;
freak at the prospects of repair$$$$.
Definitely check out some of the Benz boards - tho, for the most part, asking about a 2003 E500 there, is like asking about a 2003 Boxster here. (newer, more complicated = crap)