The link about the 20 pin connector for the Function Extension Slot, that I mentioned earlier, is actually on the iRex Forum, here:
Kudos to all concerned.
To allovertheglobe, and anyone else interested; as I said above, it will only require soldering the proper wires of the female end of a USB extension cable to the proper pins on the 20 pin plug (and perhaps a pin to pin jumper or two) to make the USB Host adapter cable--once we have determined which pins on the DR to use.
I have other reasons to go inside of my DR, hacking wise; see my Mobileread Intro. If anyone is interested in any of that, let me know, and we'll start another thread.