Just a note from someone that was in your shoes a year ago. I'd been a regular on this site for my 190SL. I was contemplating a purchase of a 300E, and started looking around at this forum. At first, I thought this car must be a disaster! Look at all the problems people have! Then I got to digging. People don't drop a thread on here with "I've got 200,000 miles on my 300E and nothing's wrong, I just thought I'd take up formum space!" The 300E is argueably the most reliable, trouble free, long running gasoline Mercedes ever made. And, once you hit 200,000 miles, you will have a hard time finding ANY other make with similar longevity! I have a '92, as do you, and most of the problems were fixed by then (valve seals, etc.). The 103 engine is pretty much bullet proof (but as you've found, not idiot proof!), and the chassis will run forever.
Last week I was in the local dealership and someone had just traded in a 300E with 192K miles on it. The sales manager mumbled/grumbled that the problem with those cars is that no one ever traded them in on a new one, they just kept driving them - and at 200K it was just getting broken in! Talk about a compliment!
So, don't let messages on this forum discourage you about your car. Also, remember that when you get stranded, no matter how long you own the car, Mercedes Roadside Assistance is available free of charge (I think 800 FOR MERCedes??). My 1957 190SL qualifies for that. Who else does that? Can you imagine if Toyota or Chevrolet did that?
'57 190SL (toy)
'08 S5500 (mine)
'09 CLK550 (wife's)
'06 SLK350 (daughter's)
'11 GLK350 (daughter's)
'03 CLK310 (spare)