Easy Install Plugin Question

[Kodaks]

Greetings everyone,
Please bear with me, I am not very experienced with plugins or php. I read the instruction in the readme for making Easy Install plugins, but when I try out my plugin nothing works. Here is the code (the file is called mybbseo.php):

<?php
function mybbseo_info()
{
   return array(
      "name"         => "MyBB SEO",
      "description"  => "--",
      "website"      => "--",
      "author"    => "--",
      "authorsite"   => "--",
      "version"      => "1.0",
      //A link to a page with update information. It should be a dynamic page because variables are passed to it
      "update"       => "--",
      //Will you allow your user to be able to update the plugin with an automatic script?
      "update_download" => TRUE,
      //Does this file have a readme? (it should be stored in "PLUGIN_NAME_readme()" function)
      "readme"       => TRUE,
      //Do you want to force people to read the readme before they install it?
      //There isn't much point in setting this to true. They need to have the plugin active before it can be used =P
      "force_readme" => FALSE,
      //EI Compatiable
      "ei"           => TRUE,
   );
}

$mybbseo_install = array();
$ei_install_index = 0;
$mybbseo_install = array();
$mybbseo_install[$ei_install_index] = array();
$mybbseo_install[$ei_install_index]['file'] = 'calendar.php';
$mybbseo_install[$ei_install_index]['find'] = array();
$mybbseo_install[$ei_install_index]['find'][] = 'addnav($lang->nav_calendar, "calendar.php");';
$mybbseo_install[$ei_install_index]['code'] = array();
$mybbseo_install[$ei_install_index]['code'][] = 'addnav($lang->nav_calendar, "calendar.html");';
$mybbseo_install[$ei_install_index]['position'] = 'replace';

//Your activation function
function mybbseo_activate(){
   global $plugin_ei, $config, $mybbseo_install;
   if(defined('EI_INSTALLED') && EI_INSTALLED){
      $plugin_ei->setupEI(mybbseo_info());
      $plugin_ei->install($mybbseo_install);
   }
}

//Your deactivation function
function test_plugin_deactivate(){
   global $plugin_ei, $config, $mybbseo_install;
   if(defined('EI_INSTALLED') && EI_INSTALLED){
      $plugin_ei->setupEI(mybbseo_info());
      $plugin_ei->uninstall($mybbseo_install);
   }
}
?>

With this plugin, I am trying to achieve a file edit in calendar.php that changes:

addnav($lang->nav_calendar, "calendar.php");

to

addnav($lang->nav_calendar, "calendar.html");

I really appreciate anybody's help. Thanks!