URGENT

Can you explain this with a little more detail?Do you get blank pages and no access to the admin area?

When I try to login, the URL set to the new one, and I get:

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

I don’t have any access to phpmyadmin or MySQL or any of that junk.

Try renaming your .htaccess file to make it inactive.For example add something like .htaccess.txt . Try loading your site now.

Internal Server Errors do usually mean bad .htaccess files.

But did you change the URL or domain in settings? See Changing The Site URL ? WordPress Codex for recovery instructions.