FeedBurner Down. Permalink Redirect? – Edit htaccess?

I made the “rookie” error of changing a post that had already been published.
I changed the headline and also the permalink.

So I shouldn’t have been surprised the next day when I learned that my Feedburner feed wasn’t working. (It wouldn’t validate. FeedMedic didn’t show any errors. But I received messages saying there was a “problem locating and parsing original source feed.” Another message: HTTP Error Code 404 (invalid path/help/wordpress_quickstart was requested.) Also “400 Bad Request” and “Feedburner was unable to process your feed.”

I CAN get a FeedBurner feed when I paste the FEEDBURNER FEED ADDRESS into my browser. But my ORIGINAL FEED there reads mysite.com/blog/?feed=rss2 (Is that last string of code an indication of what’s wrong with my feed? FeedBurner gives me the option to alter that feed: Should I?

In terms of the on-site “fix,” do you agree that a permanent redirect (from OLDPOST to NEWPOST) within htaccess is the best solution? If so can I do this through a WP plugin — and if so, which one do you recommend? If you don’t recommend a plugin, any instructions about doing a manual edit of htaccess?

(FYI, I’m using WP3.0 and Thesis Theme on a self-hosted site.) Thanks!