It took about a half hour to update Radio.root completely, register my serial number again, and set my software preferences and theme back up. Afterward, I shut down Radio, copied my old weblogData.root file over the new one in the Data Files folder, then ran the application. Everything was where I expected it to be, but it took all night for Radio to republish several thousand weblog pages and other files.
While I was tinkering with the site, I turned on the trackback feature and wrote PHP scripts that route comment and trackback URLs to the correct URLs on Pycs.Net, the Radio Community Server clone I've been using as an alternative to UserLand's server.
The reason I needed the PHP scripts was because my Radio install has a new user number granted by UserLand, 128729, that replaces one granted by Pycs.Net, 0000001. Since some of Radio's features are organized by user number, such as the most-visited weblogs report, I wanted a user number more likely to be unique. I'm publishing my weblog with FTP to my own server, so I can change user numbers without changing my site's main URL.
The reinstall appears to have solved my problems (and I don't know yet if trackback worked), though I've undoubtedly created a few new ones.
Thanks for this man, I really didn't know how to retrieve my previous postings, until I read this article and read which files to copy back to my folder.