Hello,

This would depend on if you used Fantastico (in cPanel) to install any scripts or if you manually installed them.
Most scripts have the version number in their index file or config file or in the database in manual installs.

How hard it is to update depends on whether they were manually installed, installed using Fantastico, and if any mods or plugins have been added and how far behind you may be in versions of the particular script.

The class.phpmailer.php you see in your public_html folder is most likely part of a script and would be updated with it although it could be a stand alone script. You would have to know which script is using it.

If you need assistance with any of this I would suggest contacting our support team.

I hope this helps.