It's possible to insert any kind of content in wordpress post or page using
short codes, but if you want to inject/modify content in post in more
advanced manner then there is a alternative is using filter
here i show how to do it using "the_content" filter - In your plugin add these codes -
function my_plugin_post_filter($content) {
// assuming you created a page or post entitled 'my_certain_post'
if ($GLOBALS['post']->post_name == 'my_certain_post') {
return var_export($GLOBALS['post'], TRUE ); // you can add your modification logic here
}
// else returns database content
return $content;
}
add_filter( 'the_content', 'my_plugin_post_filter' ); // filter declaration
For more filters, read the doc - http://codex.wordpress.org/Plugin_API/Filter_Reference
hope that helps to get idea before doing something big, If you have more questions, post
in forum in this site to get sorted out.