Sample .install file which enables/disables modules, features, etc.

module.install.php

<?php

/**
 * Update site to ...
 *
 * First comment is used when displaying updates to perform. Implementation of
 * hook_update_N().
 */
function xxxx_update_700X() {

  // List of modules to disable
  $modules_to_disable = array(
    'xmlsitemap_custom',
    'xmlsitemap_node',
    ...
  );
  // List of modules to uninstall
  $modules_to_uninstall = array(
    'lightbox2',
    ....
  );
  // List of modules enable
  $modules_to_enable = array(
    'auto_nodetitle',
    'breadcrumb_config',
    'captcha',
    ...
    'jcarousel',
  );
  // List of features to revert
  $features_to_revert = array(
    'blogs' => array('views_view', 'variable'),
    ...
  );

  // List of blocks to disable
  $blocks_to_disable = array(
    array('views', 'similarterms-block'),
    array('views', 'blog_list_tags-block_1'),
    array('views', 'blog_related_content-block'),
    ...
  );

  //
  // Start install / update process
  //

  // Drop unused / broken tables left by a broken install 
  db_drop_table('table1');
  db_drop_table('table2');

  // Blocks to disable. There might be a better way via an API.
  foreach ($blocks_to_disable as $block) {
    db_update('block')
      ->fields(array(
        'status' => 0,
        'region' => "-1",
      ))
      ->condition('delta', $block[1])
      ->condition('module', $block[0])
      ->execute();
  }

  // Move block around: change region of block to branding
  db_update('block')                                                                                                                                                                                             
    ->fields(array('weight' => -35, 'region' => 'branding'))
    ->condition('bid', 126)
    ->execute();

  // Change block title
  db_update('block')
    ->fields(array('title' => 'NEW TITLE'))
    ->condition('bid', BLOCK_ID) 
    ->execute();

  // Add 'Goto Google link' link
  $menu_item = array(
    'menu_name' => 'main-menu',
    'link_title' => 'Goto Google',
    'link_path' => 'http://www.google.com',
    'plid' => PARENT_MENU_LINK_ID,
    'weight' => -30,
  );  
  menu_link_save($menu_item);


  // Revert certain features.
  // See also: https://gist.github.com/becw/4121388
  features_revert($features_to_revert);

  // Disable and uninstall certain modules.
  module_disable($modules_to_disable + $modules_to_uninstall);
  drupal_uninstall_modules($modules_to_uninstall);

  // Enable other modules.
  module_enable($modules_to_enable);
  
  // revert all components of this feature
  features_revert_module('my_feature_module');

  // remove a field instance from a field collection
  // Data that is saved in the field will be removed on cron run and/or clear cache
  $field_collection_instance = field_info_instance('field_collection_item', 'field_name', 'field_collection_name');
  field_delete_instance($field_collection_instance);

  // remove a field instance from a node
  // Data that is saved in the field will be removed on cron run and/or clear cache  
  $instance = field_info_instance('node', 'field_name', 'bundle');
  field_delete_instance($instance);

}