Backup your WordPress database and files. Get ready to restore them if the "bad thing" happens.
First, test if you have SSL installed correctly. The easiest way to do that is do this:
If you get the WordPress readme.html without any goofy certificate errors, then you are fine.
Now disable any plugins that have anything to do with authentication and SSL. You don't need them.
Make another backup of your wp-config.php file and put that somewhere safe. Now copy wp-config-sample.php to wp-config.php and insert your
DB_HOST into that new copy.
See the line that says
define ('WPLANG', '');? Right after that insert these lines
Per the codex, both lines should not be needed. But that's what I have in my file. You should still insert this part
But one thing at a time.
If this tanks your installation, then restore that backup you made at the beginning and you'll be back to square one with no harm done.