We have a 98 E320 wagon. GREAT car! The v6 is poweful and reliable. Couldn't be happier with the car for the last six years.
That said, there are some things inheriant to these cars. At that milage, it likely uses oil...ours uses about a qt every 1500 miles..no biggie. Doesn't smoke.
EGR tubes get clogged and will throw a code..easy fix. May require replacement of the valve itself..again no biggie.
Be careful working under the hood...all the plastic pipes and fittings are brittle from age and heat so be ready with replacements before you begin working.
Another thing is the front end rattle..usually drop link bushings..again, no biggie.
If the cats(4) have not been replaced, they will have to be soon...usually at around 130-150k...theay are PRICEY if factory but just order generic replacements and have a local muffler shop weld them in.
If you are a do-it-yourselfer then the repairs are straightforward...if you go to the shop
Pelican has a good selection of replacement parts..I always try here first but if not available..the place in Arizona is a good source.