Hello I have a 97E420 sportsline bought it with 150k KM a year ago now i have 220k KM so as u seee i drive a lot mostly hyw though The car is excellent just do the oilchanges in every 6000km instead of the recommended 12k..I use only Castrol 10W40 for winter and 20W50 for the summer..(I ma in Canada)
I had to change the front cover seal..(common problam) and now i gotto change a seal in the power stearing..I think these are just maintenance things. BUT I had and have one mayor problam..
RUST some around the sunroof and some around the trunklid keyhole the trunklid keyhole corrosion is a known problam to mercedes so even if you are out of the warranti they might do it under "goodwill" mine was done like that so was the roof..the problam is that the roof corrosion came back again this year They will do it again but i dont feel too good about getting a roofpaint annually (other corrosion spots:drivers door lower panel,drivers side headlight holder panel..right in the front corner.)
Hopefuly this information will be somewhat useful to you..Good Luck!!!