If the trap was already replaced you don't really need to replace it again. One time deal.
However if you get a new turbo out of it, let 'em replace it again. Just hope they don't screw something up in the process. Today's MB techs are better at replacing relays and sensors than actual mechanical work.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)