My friend recently bought the same car but a 2001.
He's paid a bit over $12k in parts and labor to fix it!  In my opinion
this car was NOT worth it but he's a mercedes fan so things like
reliablity (lexus is much better) don't seem to matter.  I've noticed
german car fans are mostly in a head trip about their cars being
superior.  The truth doesn't matter to them.  Japanese luxury cars are
far better (much more reliable).  The Lexus LS460 is a great example.

Front suspension was totally shot (bushings, tie rods, shocks, pretty
much any parts that wear out).
All brake rotors were replaced.
Engine had MANY oil leaks.
I've learned on these cars (as well as other MB models) there is a
gasket in the engine near the heads that goes bad after about 100k
miles.  This gasket is hard to get to.
To change this gasket is a lot of labor (so price for this work is
high).  Several MB cars I've seen have had lousy mechanics work on
them and scam the customers by charging for replacement of the gasket
but all they do is put a bead of silicon that hides the leak for a few
months (maybe a few thousand miles).  Be very careful of who is doing
the work.

Car had lots of malfunction codes.  Several sensors were bad.  Several
problems with electrical system (this is the Achilles heel of MB, very
poor electrical systems).
To fix electrical system problems and get rid of codes was difficult
and several visits were required.  The vacuum assist for the doors was
also bad.  One door (passenger) was not able to be fixed without
changing the vacuum assy for the door.  That part is very expensive so
the mechanic suggested to just live without vacuum assist for that
door.  Several parts were changed for vacuum assist with rest of car.

I was simply shocked at the costs of repairing these cars.  I would
suggest you take this car to a good independent MB mechanic and have
them look it over very well.  You may find the price of repairing this
car just isn't worth it.  Unless of course you just have money to
waste.  If that's the case, go for it.

Good luck,

Oskar