I need help understanding the workflow that starts with downloading elevation data from the National Elevation Dataset (http://viewer.nationalmap.gov/viewer/) to importing the data in a Mathematica notebook to being able to access the raw elevation data as a matrix or table of elevations.  

I request data in ARCGrid format, and data is downloaded to my Mac in a directory/folder that contains several files and two sub-directories.  At that point, the data I need is (presumably) sitting on my desktop, but I have no idea how to import it to my Mathematica notebook from there.  The online expositions of how DEM data can be imported by Mathematica (ref/format/ArcGRID) do not help me, because the files originate from "exampledata.wolfram.com" rather than from the NED website.

I have written notebooks that take the old-style USGS DEMs (ASCII file with a 6-record header followed by a large matrix of elevation data whose horizontal position is determined by its position in the matrix).  Those DEM files were prepared for my by other people using ArcGIS to convert the files to that ASCII format.  The result is a single DEM ASCII file, not a directory of files and subdirectories.  

I need help evolving to a workflow in which I download DEM data from the NED viewer and then import the downloaded data to a Mathematica notebook in a form that allows me to operate on those data.