From what I recall seeing on the few Nordic Tugs I've been on, there is a hatch or removeable panel in the floor of the pilothouse, which is directly over the engine. So removing the engine is a matter of removing the hatch, lifting the engine into the pilothouse, turning it 90 degrees, and taking it out the pilothouse door. In theory, it should be relatively fast and easy.
On a Grand Banks, however, while the main cabin floor is made up of large panels that lift out, the challenge is getting the engine(s) out of the cabin. If the engine is a straight six like a Ford Lehman 120, I'm told that if all the side-mounted hardware is removed from the engine--- water-cooled exhaust manifold, air cleaner, raw water pump, oil filter, etc.--- the long block will just barely fit through the cabin door, assuming the helm consol is not in the way. But most of the time the usual means of removing the engine from a GB is to remove one of the large side windows in the main cabin and take the engine out that way after it's lifted into the main cabin.