Can-do,

Glad to see you still keeping those MB diesels on the road.

Have you raised the front of the car with the wheels suspended and started shaking and prying on everything to find the loose part. I have never had a track bar mount fail, which is kind of a mystery given the force it must deal with. If it is the track rod, you should be able to tell by shaking the wheel fore and aft. If it must be replaced, you'll want to check everything and replace whatever is needed while it is apart. To replace the track rod, you have to remove the spring, so you are far enough into it, it would be the time to replace ball joints or whatever might be loose.

I do understand aligning the marks to check the chain stretch. Even though it is not totally scientific, it does give an idea about stretch. If you see what appears to be four degrees, I would think that it is time to roll in a new chain. The chains are expensive, but it's not too big a job to roll one in, and it is much less expensive and less work than the consequences. I would think that you could take time to prepare and not rush into doing it though.

Best of luck,