Before you do anything else, I would go into PhpMyAdmin and 'export' the MODX database to a SQL file. That way, you'll have some version of your data and, as a last resort, you can create a new install and cut-and-paste the resource content from that file.
That said, unless your site has been hacked, there's a good chance that everything if fine and there's just a misconfiguration. First and foremost, the database credentials in the file:
core/config/config.inc.php are wrong.
If you correct them, everything may be fine.
The database name, database username, and database password are there and *they are incorrect*. (note that they are completely unrelated to the username and password you use to log in to the MODX Manager). There's a good chance that that is causing all the problems you're seeing.
If you're not sure what they should be, check with your host.
Correct those before trying anything else.
You'll know they are correct when you don't see the red error message when running
http://www.information-emporium.co.cc/setup.
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PLEASE, PLEASE specify the version of MODX you are using . . . PLEASE!
MODX info for everyone:
http://bobsguides.com/modx.html