Since the USGS Server is deep-frying the GeoTIFF format this coming Tuesday, I only have a few days to get the terrain files. However, I am unsure where to begin on the DEM.
First of all, you need the DEMs, the digital terrain model. That's urgent, indeed, as it will take a while to implement support for the the new National Map Viewer DEM file formats in TransDEM. (And the proposed one and only .img isn't even available yet!)
So, for the moment, concentrate on the DEMs and follow this tutorial:
http://forum.transdem.de/viewtopic.php?p=1065#p1065
Then, for the ground overlay you will need a map. I recommend the USGS 1:24,000 topographic map, via WMS, but you can also use a Map Tile service like Open Street Map which has less topographic detail.
For Map Tile services, follow tutorial 7 in the TransDEM main manual. For USGS WMS, it's tutorial 4. (The latter has been adapted to USGS WMS for TransDEM version 2.3)
In any case, maps are second priority. DEMs come first.
