BruceMuzz made a couple of reasonable suggestions.
Are you planning on arriving at Narita on the day your cruise departs or beforehand? This will likely shape your travel strategy. I recommend you make your way to a Yokohama hotel near Yamashita Park for a night or two prior to boarding (i.e. Hotel New Grand) and go from there (Narita Express to Yokohama Station then Minatomirai Line to Yokohama). Whether your cruise line will be operating a shuttle, I cannot say but, at least, you won't be too far from the cruise terminal for a taxi.