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None of the following constitutes a recommendation, nor is that any promise of support if it screws up. But, for my money, I would do the following course of action:
1) If you made a backup of your site before the autologin hack was applied (you did do that, right?) I personally, on my site, would reupload that backup. Now, clear the cache, clear the templates_c directory, go to admin|modules|system and update that. See if it works right now.
2) If it still does not work right, I would reupload the core (except the theme directory) and module files that you are using (assuming that you have not made any other hack changes). Now, clear the cache, clear the templates_c directory, go to admin|modules|system and update that.
3) If you made a backup of your database before you implemented the autologin hack, and you are tired of messing around with all this, you could delete your current database and put your old database (the backup) back up on your site. Of course, you'd lose the stuff from however long it has been that you've been working on this issue. This is not something to be taken lightly. But I have done it a few times. It's roughly akin to reinstalling windows from the ground up... I'm not recommending this, especially if you are, uhh, new to phpmyadmin. But, if you statements about ditching the whole site are accurate, perhaps it's time to take the chance. Due to extended time off, I can't add any further help to this reply. Others may be able to help. It may be best for you not to take this last step. As I said, I have done it with success, but it does take a degree of familiarity with mysql.
An additional "not worth a dime" suggestion: Get a book on php and MySQL and perhaps webmastering. You'll save yourself a bunch of time and agony.
MMM...It tastes like chicken! 
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