It appears, from the numbers you gave, that this is a 115 car. I'm afraid that I'm not going to be a lot of help. The only 115 car I ever had was a gas car.
If it were a 123 car, I could give you fuel filter instructions, step by step. But I'm sure you don't need special tools. There should be two filters, a large filter that looks like a spin on oil filter and a small primary filter that is no more than a screen in a plastic case. The important thing that you need to know before you remove the filters is how to reprime the system. I believe you will find a small plunger type primer pump near the injection pump. Turn the plastic knob counterclockwise to unlock it and then pump in and out to prime. Once you have located the primer pump and are sure you know how to operate it, remove and replace the filters. Then pump until you hear a hissing sound at the top of the spin on filter. It won't hurt to keep pumping after you hear the sound. Then lock down the pump knob by turning clockwise after pushing down. It should then start.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in