Thanks, that helped! I still haven't been able to get an error-free .rtf (my original goal), but after a bit of googling I was able to tweak Word to convert a plain text file to an error-free version.
Which isn't all that bad since .rtf and .txt look about the same in PalmFiction anyway.
Edited to add: Got the .rtf. PRC to Epub and back to .mobi with Calibre as suggested by JSWolf earlier, then mobi2html, then convert to .rtf and final cleanup of "hellip"s and "mdash"s in Word.