I have a 1992 300SE that has a bad fuel leak. I thought I isolated it to the fitted fuel hose and after removing it found that it was only a small part of the problem. After firing the engine post fuel line installation, I found a large leak coming from one of the fuel pumps (or what I assume is a fuel pump). I can't really tell where it is coming from, but it looks like it is literally pouring out of the brass fuel line that connects the pump to the filter. Anyone have any advice on how to proceed with this? This is a difficult job since I am having to mess with metal fuel lines and small components that are near the gas tank. Also, how do I change out the fuel pump without pouring gas all over myself?

I am an IT technician, not a mechanic!!!!!

This one is easy to answer.
Replace every line and hose that is leaking, worn, or suspected of either.
With relatively new cars you can clamp the fuel line so you don’t have to empty the tank. Since your lines are 15 years old I would replace them so clamping is not a good option.
First empty the tank as much as possible (driving and/or siphoning).
Then drain the rest by cutting the fuel line/hose to the filter and drain the remaining fuel in a container. After 15 years it is usually not possible to that the lines/hoses of without severely damaging them. Draining the tank by taking the hose of may very well result is a lot of gasoline in you sleeve.
If you can’t remove the fuel line after cutting/damaging it you have a problem, since your car won’t run. Although being a rather experienced wrencher I left this job (on a 300SE 126) to a Mercedes specialized and trained Indy. A decision I never regretted (he did).

replacement of old fuel lines is a must. I found this out when I tried to replace my fuel filter and came out with a pinhole leak in a rubber fuel line. It probably would have never leaked even though it was 21 yrs old and hard as rock if I hadn't messed with it. Another thing is that some of the brass washers won't seal properly once they are unseated. That was my problem after I fixed the leaky rubber hose. I had to buy new washers from the dealer because no auto parts store had correct washers to do the job. After new lines and washers and a lot of time trying to get it not to leak, but I just tightened it as much I could and it hasn't leaked since. i hope my story could be of some help here. It seems most of the time I need all the help I can get.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

I forgot to add on my 420sel, there was mimimal fuel leakage when the lines were disconnected and the fuel filter was off.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

I'd like to add that you should replace the ENTIRE line, not just sections. Some people like cheap out, only to spring a leak somewhere else down the line.

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1989 300E 144K

The connections you describe where the pump attaches to the filter, etc. are called Banjo Bolts. In order to seal properly, they require two washers, one under the head of the bolt against the hose end, and one between the hose end and the body of the pump or filter.

Make sure you haven't lost one of these. Also a good idea to replace these items once disturbed. Previous poster indicated the dealer as the most likely source. The washers "crush" slightly when the connection is tightened - once crushed sometimes they don't re-seal a second time.