1992 D 350 diesel leak hellp

so my 1992 1 ton leaking diesel fuel from the injector pump head the big plug in the middle of the injector lines like in these photos from Mike 93




so can I remove just the plug and replace the O ring on the truck or am I oping up a can of worms and springs N things that will go fling every ware
thanks for looking

Here is a parts diagram.

VE pump