A forum devoted to the W123 cars is a GREAT idea, Vince. I am 45 years old and have owned many cars over the last 29 years, including three 300TDT wagons. I believe that the W123 series is the quintessential Mercedes, designed and over-engineered before the accountants in Stuttgart (now Detroit) changed the design objective from excellence to profit.
The W123 cars are handsome and distinguised as they were the last chassis line with coachwork featuring REAL chrome (not painted plastique) and designed before the advent of wind-tunnel testing.
I particularly love the turbo-charged diesels. The trick is finding one with a FULL service record and a conscientious owner. I've determined that, ideally, you should buy a diesel from the WIDOW of an engineer who had the car from new and maintained it on schedule (the wife always hated the diesel, and now the car now reminds her of him), for < $4,000.
One thing I've found is that these diesels do cost money to maintain. My current car is a 1985 with 150,000 miles on it. I purchased it from a guy who owned five cars and had run out of garage space. I had been looking for a 1985, which was the last model year for the W123 chassis, and theoretically the most refined 300TDT. Cosmetically, the car was in excellent condition, having been garaged its entire life. Mechanically, the engine didn't smoke on hard uphill acceleration, and the transmission didn't clunk heavily between 1st and 2nd gear (warning signs I had learned to heed from the prior two cars). The owner had thirteen years worth of service records (he was the second owner, and didn't receive records from Mercedes of Greenwich, the dealer who sold him the car). During the 13 years he owned it, he spent more than $20,000 on maintenance with Mercedes of Greenwich! I paid him $6,900 for the car (his asking price, and high, in my opinion) and, within sixty days of owning it, spent $700 on rust removal, $150 to have the a/c system re-charged, $3,250 on maintenance (from an indie German car shop in Mamaroneck, NY), and $750 upgrading the sound system (I recommend the new Becker 4602 unit for this purpose, which can be bought directly from Becker for $450)
The garage want to convert the a/c from R12 to 134, but tells me that's another $500-$750 job. Since the system is still cold from the re-charge, I'm going to put off the a/c upgrade as long as possible.
I'm looking forward to reading the threads in this forum. When I see someone driving a W123 wagon, I always wave as if they're a family member!