Right below the injectors on the driver side they have a wire held by a small nut you should have 5 of them if it's a pre 86 model
Dexron III
The radio code should be on a card in the glove compartment. If you do not have the code you will have to call the dealer to get it.
The fuse diagram for a 1984 Mercedes 380 is located in the service manual. It outlines where each fuse is located and the component it is attached to.
The spark plugs are located right under the exhaust manifolds of both sides of the engine. You should just follow the spark plugs wire from the distributer.
The ignition module is located in the distributor under the rotor, it plugs in.
Which one? That's a good place to start.
made onto the top of the starter/
The same thing happened to my 1984 300SD. I removed the instrument cluster (speedo, tach, fuel guage, etc.). Using a hammer, I tapped firmly on the lock assembly while twisting the key in the tumbler.
The ignition module is located in the distributor under the rotor, it plugs in.
Buy a Hayne's manual for the Mercedes diesel or a Chilton's manual for Mercedes (it has a 123 Mercedes on the cover). It will show you how to change the inline fuel filter and the main fuel filter.
depending on the engine size they will be located in the sides of the heads. look for a rotor cap and 6 or 8 big wires, depending on the engine, then foller them rihgt down to the spark plugs.
If it runs fine on the level but loses power on the hills, check the small fuel filter and if it is OK replace the big fuel filter. Do it yourself for about $10. A dirty filter keeps it from passing enough fuel for a hard pull.