OK, I did it. I changed computers with Radio Userland. I knew it was going to be a chore, but I got through it. This article pointed me to some useful scripts, including one called myFixFilePathsAndAddresses that helped with adjust the internal file paths stored in Radio.root because the installation path on my new computer was on a different drive letter (C: --> D:).
Here's the dirt on myFixFilePathsAndAddresses:
This script is an improvement to the one UserLand provides in the workspace.userlandSamples table. If you move your Radio UserLand folder to another location on your hard disk or to another computer then your copy of Radio UserLand will not work. That is because there are many internal references to absolute file paths within the Radio.root. To correct these references download this script and open it from the Radio File > Open menu. Then run the script. It will ask for your prior file path, the default choice should be correct. When the script finishes everything should work again.
I copied my entire www folder from the old installation, the Data Files folder, and Radio.root. That seemed to do the trick for most things, but I had to tweak the preferences a little to restore my old settings. At some point, everything popped back into place, but I'm not exactly sure what order I did things in, so I can't give an explicit tutorial here. The articles mentioned above should help though.
I'm finding though, that since I moved my Radio installation from an always-on static IP address to a frequently-moving laptop computer, that there are certain disadvantages to not being able to remotely post from anywhere. Having a server handle upstreaming in the background while I go about my daily life can be a plus sometimes. Hmmm... We'll see how it goes.