Well... our 1999 ML320 (W163 body) spend 13 years with my family.
During those 13 years it had couple of parts failing.
Total cost of new parts about $350 or less than $30 a year.
How you take that for one of the worst MB?
When MB did have few oops over the years, from top of my head I recall only 2 big ones.
You got off lucky though -- 1998-1999 and very early 2000 ML had one gigantic glaring flaw in it -- they used a central computer for damn near everything, from AC to door locking/unlocking to remote receiver to immobilizer to windows, alarm, etc etc etc... and it's called AAM. AAM likes to fail, and fail often.
AC stops working? You need new AAM. Windows, or door locks stop working, or car stops turning on, etc? New AAM. and since AAM is a theft relevant part, only dealer and/or locksmith credential mechanic shops can order it.
Dealer's SOP was to bundle new keys and/or new ECU when they ordered AAM, so the final bill often exceeded $3000 when all was said and done. I bought a beater ML -- and it has that problem right now. It's been nothing but headaches, and I'm trying to find out what I can do.
Later ML's they separated the immobilizer from the AAM to its own dedicated module, so when AAM fails, it's not so expensive to fix.