one-piece touching means, that particular part is repainted, and it does affect resale of a car, however, buying such a car is not a problem unless and until the car is not Accidented....as touching can be done due to scratches , etc. as well.....
but it is advised that you better go with some mechanic that is trustworthy, or someone you know who knows about cars well so that you may not be chated upon!..