Engine swap (successful one) is not a bad thing, it increase your car's life and it's original L13A engine with registration on book.
As far as car price is concern, I have touched Islamabad market for same model with matching condition is around 800K, so the demand is very much realistic, justified and including engine change impact discount (which it shouldn't be).
It is running successfully on newly installed engine since October 2014, there is nothing to be hidden from potential customer / future owner.