Well, as I have heard numerous times, a "cheap" Mercedes is the most expensive thing you can buy!! This might be the case here but you will be so much more "educated" when you work through your problems.
Your rough idle - Check each and every fitting on the vacuum system and I am sure you will find some that are cracked and hard. Vacuum leaks are BAD! For about $75 from the Benz dealer and a few hours time, you can replace each fitting. Then I would suggest that you look at the check valves that are in the vacuum system. I bet you have at least one that is cracked, especially if they are all original.
Your vibrations can be a number of things, again, especially if this car has original parts. Motor mounts are one thing to check. The transmission mount is another to check. The center carrier bearing and mount is probably toast also. Check your flex discs also. I have a '91 300E with 189K on it and have had to work through each one of these items. You can get a "vibration" feeling also from the exhaust pipe mount that is attached to the transmission. I would bet that the rubber parts in that mount are gone.
I would suggest getting the mounts from the dealer, there is a difference. The other items you can get from our parts supplier from this website or ***************.
Good luck!!