I have an '87 SDL with 119,000 miles. Some of you issues I have had. Recently I had a similiar oil leak... small but screws up the garage floor. It was diagnosed as a crack around the timing chain cover. My machanic sealed it from the outside and there are no leaks now. I also had a clogged valve around the turbo that had affected performance ever since I got the car (around 102K miles). Once this was fixed, the performance is incredible and we LOVE the car. The transmission shifts much more smoothly since that valve was replaced. It was clogged with oil. I don't have the technical details with me but maybe someone can fill in the blanks.
We also replaced the tie rods and it's just an incredible traveling car.