Thanks, Günter,Perhaps I'm going about things the wrong way. Instead of trying to use XeTeX, perhaps I can just use one of the engines that is already built into LyX.
So, with my sample document, set to "utf8-extended" encoding, if I try rendering it using the built-in pdflatex engine, I get a bunch of inputenc errors, like the following:
LaTeX Error: Command \textdasia unavailable in encoding T1. Any thoughts? -Erik