accidentally changed the PS directory, and now can't use the backend

[zomigi]

I'm having problems with the base directory not being correct (causing the logo to not show up and scripts to not work), so I tried changing the "PS directory" in the Preferences area of the admin tool. That didn't fix the base directory problem, so I tried to change it back to "/", but when I click save, it tries to go to the test directory I put in previously, so it won't save, and now I can't fix it!

Can someone tell me:
1. how to change the PS directory back to "/" manually
2. how to change the base directory so that the images and scripts will work

Thanks!

[zomigi]

Ok, I've already figured out issue 1. Downloaded config/settings.inc.php and changed it manually.

But, I'm still having problems with the logo showing up and some of the scripts working. The URL to the logo (changed to mask my client's name) is:
../themename/http://www.example.com/img/logo.jpg

The URL should be:
/img/logo.jpg OR
img/logo.jpg

I need to get the "../themename" out of the URL, which is hardcoded, as well as the site domain name, which gets put in with either {$content_dir} or {$img_ps_dir}

Please help!