Pretty hard to mess it up actually, just pull the loopy connecting wire off the old plugs, remove the ground strap from the front plug to the engine and put a wrench or ratchet on the old plugs. New ones go right back in the same way except using the new wires and NO ground strap on the front. Should really only take 30 minutes (or less) to complete. I wouldn't even bother removing the injector hard lines, but then I'm lazy like that. I also like to add a little anti-seize compound on the threads of the new ones to make it easier next time. If your b/f is worth his salt, he shouldn't have any trouble with it. But like I said, it's easy and you could easily do it yourself.

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'79 300D, Ivory "Gunther" ......going
'81 300SD, Metallic Blue Silver, The Grey Ghost.....going
'87 300D Turbo ...gone
'05 CDI.... gone