The wrong oil was used? I'm assuming they mean the wrong viscosity, but I'm unsure how they could tell this during the oil change...unless it was ATF or something. Where did you get this oil change?
If it was an oil issue that caused damage, the damage is most likely already done, and putting the "correct" oil in there will not fix it, but may prolong the life. If it was ticking from under pressurized lifters, then the correct oil would fix it. As others have stated though, I would definitely get a second opinion. Ticking can be caused by LOTS of things, and to assume wrist pins is a bit of a stretch. Also, to an untrained ear, ticking and knocking sound similar. Knocking = $$$.