Thanks, folks -

1991 model is something to consider it seems.
The 300 models with the six would be preferrable as I am partial to german inline six engines. (as well as Ford 300 straight six). (One of my cousins just spent around $5G on his 420SEL from a chain reaction damage that started with the timing chain, so I'm leery of being able to afford the upkeep on a V-8 benz.)
With the SEL models, heck, I'm not worried about the parking issue.
Yes, my father's '90 300SE fuel economy gauge dips into the redzone when taking off but it's a great highway cruiser and very quiet.
I'll have to poke around in the engine compartment with a bright light to see if there is any oil leaks as described.
I hope Mike's guess is true about the improvement in valve quide seals, etc. starting with '90 model year.
I'll report back with what I find in the '90 SE.
Thanks again for the feedbacks and if someone can confirm the improvements made in 1990 I would appreciate it.