Not a pretty sight. You will find this picture typical on many of the V8 gas engined Mercedes built in the 1970s and 1980s. If the car has been exposed to road salt the rust will make it very difficult to even get the parts off the car. From my experience this is one of the maintenance areas most often neglected and as these V8 cars continue to age, it is not uncommon to find back end fuel delivery components looking like the ones in this picture!
Problem & Solution
Common among these chassis:
Here is a 450SEL 6.9 that had been neglected to the point where the engine would no longer fire or start. Needing replacement are rotten and aging fuel hoses, rusty fittings, broken rubber shock mounts, plugged fuel filter, weak and noisy fuel pump, inoperative check valve, and a bad accumulator.
Even if you go to replace just the filter you may have to deal with hardened fuel hoses, rusty clamps, noisy fuel pump, etc. Overhaul and replacement of these parts can be labor intensive and expensive if done in a shop. The work is not difficult so if you are willing to take on the work yourself you can save big $$$. You don't even really need instructions. Just drain the tank, remove the entire fuel pump assembly, inspect componets, and order what you need. The most challenging part of the operation is keeping gasoline from running down your arms. Do the draining outside with a fire extinguisher at your side. VERY IMPORTANT - have some good hose clamp pinch tools on hand to prevent the gas spills and drips. Some parts may have to be purchased from Mercedes.
The goal will be to turn what you see above into what you see below. This will require some elbow grease, new fuel hoses and clamps, new filter, new check valve, new accumulator and some miracle paint to stop the rust permanently. 
If you do it right it will make service in the future a lot easier. Just think how you will feel when you get it back in the car and it looks like this... :-)
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