Yes—if the mirror lifts but the shutter curtain remains closed throughout the exposure, that strongly points to a stuck shutter. That would explain the nearly black files with slight variation/noise.

The safest recommendation is to have the camera inspected by a Nikon-authorized repair shop. A shutter assembly is not generally considered a DIY repair for most users.

One community member reported a temporary revival method: with the lens removed, set a long manual exposure and gently but firmly tap the base of the camera during the exposure until the shutter opens. However, this is an at-your-own-risk workaround, not a proper repair, and could potentially worsen the problem.

So the practical answer is: it’s very likely a shutter fault, and professional repair is the proper fix.