I just completed a single row chain replacement on my '83 380SL. It too was (reportedly) replaced by the previous owner but as he couldn't supply any proof, I took it upon myself to tackle this job. I'm not an experienced mechanic and it was (one of) the most difficult that I've done to date. Although it references a "double row", this YouTube video was instrumental in helping. https://youtu.be/7DQdGlSLMLM

As with any job, it's always good to know what parts you'll need prior to starting and the video opens with a complete overview.

As Benz Dr. suggested, I too replaced the oil filler tubes, valve gaskets, belts and generally cleaned up the alternator, power steering pump and related brackets.

The "double row" appears much easier as it can be purchased with "circlips". All the "single row" replacement chains come with a "master plate" and "master link"...which need to be properly peened. I'd purchased a (relatively) inexpensive chain riveter off Amazon, and it was a complete PoS. After a number of different (failed) methods, I wound up paying a mechanic (took :02 minutes with his specialized MB die/chain riveter) to join the master link. Simply, I didn't trust my abilities with this part because simply, if the link isn't properly peened, then the chain will break apart.

The only other advice I would offer is to be extremely careful with removing wire from the distributor to the ignition module. The distributor had to be removed to get to the pin holding in one of the rails and the wire was so old and brittle it fell apart in my hands..but in the process, likely damaged my distributor. The pickups inside the distributor are quite delicate. Simply, after replacing the guides and chain, I had to battle finding out why it wouldn't turn over and it came down to the distributor.

I've been benefitted greatly by contributors herein (thank you all)...so hope my perspective helps...I'll keep an eye on this thread to see if there's anything further that I can offer.