The 2.8 liter engine in 93 was a 3.2 liter engine with less displacement and about 20 less horsepower. Both are what Mercedes calls a "104" engine and that engine series started in 93 in the USA. Double overhead cams, 4 valves per cylinder and an electronic fuel injection. Previous models had one overhead cam, 2 valve per cylinder and a mechanical fuel injection with electrical tweaks on it.
Between the 2.8 and 3.2, most engine parts interchange. I have heard the 2.8 transmission is a little different but I am not sure.
In other catagories, the 3.2 had a lot of things standard that were extra on the 2.8. The two most significant things I remember is the 3.2 had leather and memory power seats. I believe the 3.2 may have had wipers on the lights and the 2.8 did not. New, the 2.8 cost about $5,000 less than the 3.2.