How to write a module that appends data into body of a chosen content type?

Hi everyone,
As the title suggests, I am writing a module that I would like to append a voting mechanism to a content type selected by the admin in the settings page. Here's what I have so far:

<?php
/**
* Valid permissions for this module
* @return array An array of valid permissions for the jquery_vote module
*/
function jquery_vote_perm() {
  return array('access jquery_vote content', 'administer jquery _vote content', 'create jquery_vote content');
} // function onthisdate_perm()

/* Admin settings */
function jquery_vote_admin() {

  $form['jquery_vote_maxdisp'] = array(
    '#type' => 'checkboxes',
    '#title' => t('Node types to append voting mechanism to'),
    '#default_value' => variable_get('onthisdate_maxdisp', 3),
    '#description' => t("Select a node content type to append the voting mechanism to."),
    '#multiple' => TRUE,
    '#default_value' => is_array($field['jquery_vote_maxdisp']) ? $field['jquery_vote_maxdisp'] : array(),
    '#options' => array_map('check_plain', node_get_types('names')),
    '#required' => FALSE,
  );

  return system_settings_form($form);
}

//Creates a link to the page on the admin page

function jquery_vote_menu() {

  $items = array();

  $items['admin/settings/jquery_vote'] = array(
    'title' => 'Jquery vote module settings',
    'description' => 'Description of your jquery vote settings control',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('jquery_vote_admin'),
    'access arguments' => array('access administration pages'),
    'type' => MENU_NORMAL_ITEM,
   );
  
  $items['testpage'] = array(
    'title' => 'Jquery test page',
    'description' => 'Just a test page',
    'page callback' => 'jquery_vote_all',
    'access arguments' => array('access jquery_vote content'),
    'type' => MENU_CALLBACK
	  
  );

  return $items;
}

//Creates page that has the voting mechanism

function jquery_vote_all() {

	$page_content = '<div id="rating">Container</div>';
	
	
	return $page_content;
	//print_r($page_content);
	
}

//Adding jquery

function _jquery_vote_js() {
	    drupal_add_js(<<<EOT
 $(document).ready(function() {
		 
//insert custom Jquery code here


}

//Initializing the jquery

function jquery_vote_init() {

  _jquery_vote_js();
}

All I managed to do is to create a page called testpage so far that has the line <div id="rating">Container</div>. That triggers my custom jQuery which enables a voting mechanism. Is there a way to append that line to a chosen content type? The settings page (admin/settings/jquery_vote) lists ALL content types, but once selected and submit button is hit, how do I select the content type?

I'm a newbie when it comes to creating modules, and any help is greatly appreciated =). Thanks!!