There should b e a version of dem2topo out there that has idl built in -- you just have to click the "run idl?" and move on.
Dem2topo takes geotif formal files ( tif extension). The usgs server now just loads GridFloat (flt), ArcGIS, or image format, so you have to use the scripts I mentioned (or directly use GDAL_translate) to covert from one of those formats to tif.
Both GPSMapEdit and Global Mapper cost money (the latter a lot more) if you want them to save anything useful. Both also require that you have cGPSmapper installed to make the img file for upload to your GPS.