This is my first time attempting to make a Wordpress plugin. I would like to insert three lines of code into the `post-template.php` file under `wp-includes`. I am thinking I will need a way to override the function, in this case, `get_the_content`, so that it calls my plugin's version of the function instead of the default one. 

Based on what I've searched, it is not a good idea to override the core files so I'm hoping there is a simple way to modify the function through my plugin.

What would be the best method to go about doing so?