Wow! Barnez and Mark, great news! I figured out how to delete using FTP (it's actually REALLY simple!), and then I reinstalled WF 5.0.2. Everything's working fine, and my settings were even still the same (though I did enable the Falcon Engine).
So, I used this link: http://tinyurl.com/o4b3oxq to help me. This link is also good: http://tinyurl.com/ol9fzqb (but I didn't use it).
Thank you both for all your help! The only mystery that remains, however, is why it failed in the first place.