wp-admin serious problem

Greetings. My blog is located at
http://www.niceguysfinishthird.com/index.php
I was doing some tweaking this evening, and something I did seems to have utterly and completely hosed both my site (all layout is now gone, replaced by pretty much straight text) and my ability to edit – my attempts to access http://www.niceguysfinishthird.com/wp-admin are met with a 404 not found. First, my particulars:
– wordpress 1.2, installed via Fantastico with no problems
– Firefox 1.0
– Win XP
Now, an explanation of what I think happened. When I started my WP blog, I moved over from Blogger. In doing so, my homepage became suffixed with /index.php for some reason (I don’t care why, that’s not my issue…). But, the header of my blog, when clicked, returned people to http://www.niceguysfinishthird.com (no index.php).
I was attempting to fix this particular problem, and in doing so I went to the Options menu in wp-admin. There are two lines there, one saying “WordPress URI” and one saying “Blog URI” or something like that. This is what I did:
wordpress URI
OLD VALUE
http://www.niceguysfinishthird.com
NEW VALUE
http://www.niceguysfinishthird.com/index.php
BLOG URI
OLD VALUE
http://www.niceguysfinishthird.com
NEW VALUE
http://www.niceguysfinishthird.com/index.php
It seems to me that changing the BLOG URI value was a success, but changing the wordpress URI? Not so much. The question I have, then, is how can I get back into http://www.niceguysfinishthird.com/wp-admin to fix this problem? Changing the wordpress URI seems to have hosed me completely, and I know it probably wasn’t so smart, but I was…well, you don’t want to hear my excuses.
Is there anything I can do short of reinstalling, and if so, what would that be? Thanks for your time…
Paul