Someone is going to paint me as a troll, but I'll risk the public scorn... 1997-1998 was the first transition year of the "old" Daimler-Benz to the "new" Daimler-Chrysler (DCX) that meant operational changes in Stuttgart. Early years of the merger saw a power struggle between the two companies - capitolism versus craftsmanship in my opinion. Eventually the Germans won, but not until after Mercedes product quality dropped into the basement. You could not pay me enough money to drive an MY97 or MY98 Mercedes!
Anyhow, compared to your older vehicle.. a 1997-1998 E will likely be inferior in the following areas:
* Interior materials quality (leather, cracking dashboard)
* Engine mechanical (harmonic balancer failure is common)
* Electronics quality (switches, motors, audio equipment)
* A/C compressor (approx. $900 - $1000 USD)
Most failures are reported in the 80k - 120k mile range from my reading.
Keeping in mind this is a site for disgruntled owners... the following link enough interesting horror stories, especially for recent (2003) models:
http://www.mercedes-benz-usa.com/e_class.php
Hope that helps in some way :-/
-DM