The oil will be there forever, no matter what he does, so carpet replacement is the only way to go.
However, at the same time, make sure he gets rid of that copper line and goes with the original nylon line. that's why it leaked in the first place. Copper has a much greater crush specification than nylon, and you really have to torque the fittings to get it to seal correctly. Not sure if "crush specification" is the correct terminology, but you get the idea.
Plus, copper is subject to cracking and breaking with age, so go with what the factory went with. Nylon.