I bought a 1984 300D this weekend. It has a little over 190,000 miles. It does have vacuum system problems, 2 windows will not go down, and it will not shut off unless the doors are all locked. The other problems are that the radio doesn't work and the a/c needs charging.
The owner seemed to be a really nice guy and was very upfront and honest about everything.

My question is what maintenance should I have done now?

The previous owner was very organized with the maintenance records. For the three years and from his records he had the oil changed regularly and had the a/c charged annually and when he bought it he had all the belts replaced.
I read the brake fluid should be replaced annually and the engine valve clearances checked and adjusted every 15,000 miles or 15 months. So I thought I would have that done. What else should I have done to get the maintenance up to date?

I have read the owners manual and am now reading the haynes manual the previous owner gave me. I have very little mechanical knowledge, but I want to learn so I can do most of the maintenance work myself. Where would be a good place to start?