Miles,

Congratulations on the "new" car.

I have driven beaucoup miles in the 123 cars, the manual transmission 240D in particular. I will take your questions in order:

The odometer is easily fixed by you if you are willing to give up the use of the trip odometer. What happens is that the trip odometer wears and puts drag on the mechanism. To easily make the main odometer function again, you will find a plastic spur gear on the side of the mechanism that mechanically connects the trip odometer and the main odometer. Remove that spur gear and your main odometer will function just fine.

I have used Chevron Delo 400 multigrade for many years and saw my original 240D engine go 380,000 miles by changing the oil and filter every 3,000 miles and draining the oil an extended period of time with the engine hot when pulling the plug. I personally would not change to synthetic at this stage of the engines life. Delo is designed SPECIFICALLY for diesels and does a great job of handling the soot problem present in diesels. If you do decide to switch to synthetic, I strongly recommend that you use Mobil Delvac One rather than regular Mobil One. The Delvac one, like the Delo is designed and blended specifically for diesel engine use to handle the soot dispersal.

I have used Mobil One 5W30 in my 240D manual transmission with great success. The car has 533,000 miles and the manual transmission still works perfect and has never been apart. Although some of the 123 owners manuals list ATF for manual transmissions, these manuals were written 20 years ago. In that time ATF has gone through major changes and improvements intended to help AUTOMATIC TRANSMISSIONS. As a result, modern ATF's are not healthy for many seals found in units other than AUTOMATIC TRANSMISSIONS. If you still insist on using ATF in your manual transmission, I strongly recommend finding some Type A transmission fluid. It will do away with the risk of losing a seal. Changing the lubricant in this transmission is extremely simple. Simply put a drain pan underneath and remove the fill plug first. It normally requires a 14mm allen, but is easily removed with a pair of channel lock pliers. After the fill plug is removed (you remove it first to ensure that it will come out and you don't get stuck with an empty transmission that you can't refill) remove the drain plug at the bottom. Once the lubricant is drained, replace and tighten the drain plug, then fill through the fill plug with Mobil One 5W30 or whatever you decide to use, then replace the fill plug and tighten.

As a previous poster pointed out, you should probably check the shifter bushings, but I think the long throw is just different than whatever car you are used to. You will get used to it.

The reason your paint looks so good is because in the early eighties these cars had a solvent based clear coat. It was probably the best paint ever put on a production car. In the late eighties the tree huggers forced the car companies to move to a water based clear coat that is one of the crappiest paint ever put on a car. My 240D looks better than my 300E for this reason and it has never been waxed, the solvent based clear coats just don't require wax.

My 240D has European lights and I love them, but they are not as necessary on the 123 as they are on the 124. The 124 has HORRIBLE US lights. The 123 has sealed beams. There are some excellent sealed beam replacements on the market that use an H4 bulb. These are inexpensive, very easy to install and do a great job. Unless you want Euro lights for how they look, the Hella replacements would provide great light. Actually now that Halogen sealed beams are so readily available (they weren't when these cars were new) they do a very good job.

Enjoy,