I have a 1984 300TD. I have a oil leak in the drivers side by my feet and I also have a very load squeking sound while accelerating which stops after some time. Many more threads will come since this car has many miles on it.

on driver's side is probably the oil pressure gauge connection. These cars direct-read oil pressure by sending a tube to the instrument panel.

You must pull-push the instrument panel out to gain access to the connection. If you are lucky it simply needs a gentle tightening. If you are unlucky, male or female connection is split from overtightening and needs replacement.

Regardless of whether or not the gauge has been damaged from over tightening, you need to get a 10MM line wrench. A line wrench is a special wrench generally used for hydraulic lines. Use the line wrench to hold the stationary bolt while you loosen (or tighten) the disconnect line using a regular 10mm open end wrench. If you do this method, your oil gauge will give you many miles of good service; if not, you will continue to suffer from oil leakage issues.