Fix outdated Wordpress plugin (PHP) to function flawlessly with the current version of WP

For several of my Wordpress sites, I use a plugin called Autoblogged, which is no longer maintained or updated. It does indeed work with the current version of Wordpress (3.5.1), except for one major quirk/annoyance: Whenever the plugin is activated, a short error message is displayed at the top of every page: "Service Unavailable. The requested content is either temporarily unavailable or not handled by this server.", followed by the actual page. This is of course unacceptable to myself and my readers. Simply stated, it looks quite unprofessional and must be fixed. Through trial and error, I know exactly which .php file is the culprit. Unfortunately, it happens to be the main file, and I don't possess enough PHP skills to patch it myself. The file size of the .php file is 173 KB, or slightly over 4,000 lines of code. I need a Wordpress/PHP expert to nail down the faulty lines of code within the plugin and fix them, so that the plugin works as intended again with my web host. I will provide a test environment (Basic Wordpress site with the plugin installed, admin rights), so that the solver can log in and edit the plugin code from within Wordpress. Optionally, I can provide ftp access as well, if needed. I will gladly answer any of your questions in the discussion, but not via PM. Thanks.