New 300D Owner - Need Advice!

I need some advice. I bought an '84 300D after doing a lot of research. This is my first diesel. The reason I wanted a MB diesel is because I was looking for safety, reliability, longevity, and fuel economy. Because I did my research, I expected it to have slower acceleration than a gas engine. Everyone says I drive like an old man anyway so I didn't think the slowness would be a problem. And this car is very, very pretty. But I'm about ready to take it back to the seller because it's driving me crazy. I'm looking for advice before I take it back.

It is slow. Very slow. I would say dangerously slow. It's a turbo too, so I expected that to help out a little. It doesn't seem to. I honestly don't know how I'm going to pull onto the highway under heavy traffic. I don't even have enough confidence in it to pull onto a major street unless it's at a traffic light. Is this me? Is this just something I have to get used to? Are there any adjustments I can make or things I need to look at to make sure it's not the car? Never having had a diesel, I'm not sure what is normal. How slow is too slow?

And the shifting. It's an automatic but I think it shifts very hard. Each and every shift to a higher gear is punctuated by a loud clunk. Again, is this normal for the car or do I have a major transmission problem?

I'm not even going to get into all the little things inside of the car that don't work. The passenger window just got stuck in the open position on me this morning (and it was cold out too). This little knob is missing, that little knob doesn't work.

I have never bought a car this old or with this many miles. I have wanted this car for a long time and now that I bought it, I wonder if I did the wrong thing. I don't know if I just need to find some patience or if I bought a lemon. I really feel like I'm in over my head here.

This morning I got so annoyed with it that I turned around, went home, and drove my Taurus wagon to work. How sad is that?