Quick google search for “osm dxf”, told me that the best bet is to save the DXF as a shape file and then convert that to OSM xml. As I said the best way to solve this is to use the mailinglist.

I’m not sure what you said in your latest post, but just to clarify if you convert it to a GPX you are very limited in what you can get out of it AFAIK. The OSM xml file format is what describes our geodata.