That's great news. I was concerned from what I had read that using the Topsider eliminated the possibility of removing oil while hot and mixed.
Yes, I have magnetic drain plugs in my later MB's. I can't find one for the 123 diesels anywhere though. I get the ones for the 124 chassis and later at Pep Boys.
A magnetic drain plug is a very good add on. Not only does it catch much of the microscopic metallic particles. But every time you change the oil and wipe it off, you can tell if there is anything crazy going on. There is always the slightest amount of grey particulate wiped off the plug. If there is more than you usually see, it's time to keep a closer eye on things.
Have a great day,