Here's an edited Google Map of the Narita area:
The city square and train stations are at the bottom left. Omotesando street leads from the town square to the Narita San Temple, the big green area at the top of the map. The distance is about one kilometer (a little over half a mile).
And, here's Jetstar's Narita Layover Google Maps page:
View a larger version of the above Narita Layover Map in a new window with the points of interest labeled and described.
Here's a link to a very large file (1.3MB) which is a scan of a recent Narita tourist map. Best to just download this rather than viewing in your browser: Narita Tourist Map