Sorry to hear this. I have never heard of a tear happening naturally on the 370z roof, unlike the 350, so to me it does sound like it was vandalised or something has accidentally caused the damage. Only issue I have seen is wearing of the roof above the doors by the windows where the roof didn't align which is different to your problem.
Unless they are roof specialists with experience of the the 370 roof I would steer clear. The roof is fitted via laser alignment in the factory, any slight misalightment due to replacement or adjustment will likely cause the wearing issue above. I know of one member who went through 3 different roof fits this way.
Nissan enginners go through a specific training course to deal with roof issues so I would be looking for one of those. One person to contact is Sly at kaizer motors to see what he would recommend.
A quick fix patch or something, although not ideal, may be a safer and far cheaper option.