I kinda thought fuel pumps were mostly plastic these days, but I'm also well aware of the fact I know NOTHING (yet) about diesel fuel pumps. I do know that my fuel filter is between the tank and pump, though with a gravity feed to the filter. What I do know however is that metal shavings in ANY fluid that has anything to do with an engine is NOT a good sign if it came out of the engine or it's fuel supply. The screens on the injectors SHOULD stop it as last resort, but that much trash would likely stop them up if it makes it past the filter. If that came out of the filter bowl, then the filter's doing it's job. Hopefully it's just diesel you bought (which is bad enough) and didn't come from your machine. I can't think of anything upstream of the filter that would have that much trash in it. If that came from between the filter and the pump, though, if the pump hasn't grenaded yet, odds are it won't be long.I saw that as well, but I assumed that the metal shavings were in the pan before he drained the fuel into it. The pump could have grenaded as well though, resulting in a bunch of metal and plastic debris in the fuel system. If that's the case, hopefully the filters prevented any of it from getting to the engine.
If the engine was said to be 'fading' on heavy throttle, I think I'd go ahead and yank the injectors for a good cleaning, or just replace them. It doesn't take much trash in an injector to be a BIG problem. You do you, though.