Wow! Thanks for the awesome link to Droid X Dissected! | Droid X – Blog dedicated to Droid X News and Accessories!
That was just what I needed!
See those two little square whitish things at the top of the "motherboard" near the camera. Those are the RF antenna connectors. The white wire (near the camera) referred to in the link is very likely the antenna itself or leads to it. The other connector is probably the "external test antenna" port I'm looking for. So now, a small hole drilled in the back near the battery removal strip should allow me to plug into that port. Another small hole in the battery cover just above that will get me to the outside world and to my antenna amplifier. Strong signals here we come!
Now to find the antenna adapter cable that plugs into it. I think I know where to get that.