Catchable error

I am getting the following message when I try to login into my admin page. My whole website is down as well. How do I fix this? I am not a techy person

Catchable fatal error: Object of class stdClass could not be converted to string in /home2/bensonpa/public_html/cherienew/wp-content/plugins/ik-facebook/include/lib/GP_Facebook.php on line 51

The page I need help with: [log in to see the link]