Glad to be of service, and glad that you got it straightened out. I learned all of this through FT, too, so just passing it on. You can probably find out a lot more about this by searching "Guaranteed airfare" and/or "refare" or "reprice" ... there's quite a bit of info.

In the future, if you have no upgrade at stake, refaring online is often the easiest way to go, although it doesn't always work (e.g. on a complicated itin). The online refare tool will properly apply the guaranteed airfare rule and treat your vouchers/e-certs properly (or it has IME, anyway).