Set Custom Post Type in Widget Settings for use in Widget

Set Custom Post Type in Widget Settings for use in Widget

I'm trying to dynamically list all of CPT's in a dropdown, set one in the widget settings and then echo that value in the actual widget output. I can't seem to get it to work though. I was trying to use get_post_types which might be the correct way to achieve this, but I couldn't manage to use the value in the actual widget.
My Base Widget code is:
<?php
/**
 * Add function to widgets_init that'll load our widget.
 * @since 0.1
 */
add_action( 'widgets_init', 'xyz_search_resources_widget' );

/**
 * Register our widget.
 * 'Example_Widget' is the widget class used below.
 *
 * @since 0.1
 */
function xyz_search_resources_widget() {
    register_widget( 'XYZ_Search_Resources' );
}

/**
 * Example Widget class.
 * This class handles everything that needs to be handled with the widget:
 * the settings, form, display, and update.  Nice!
 *
 * @since 0.1
 */
class XYZ_Search_Resources extends WP_Widget {

/**
 * Widget setup.
 */
function XYZ_Search_Resources() {
    /* Widget settings. */
    $widget_ops = array( 'classname' => 'xyz_search_resources', 'description' => __('Displays a Search for Resources.', 'example') );

    /* Widget control settings. */
    $control_ops = array( 'width' => 300, 'height' => 350, 'id_base' => 'xyz-search-resources' );

    /* Create the widget. */
    $this->WP_Widget( 'xyz-search-resources', __('XYZ Search Resources', 'xyz_search_resources'), $widget_ops, $control_ops );
}

/**
 * How to display the widget on the screen.
 */
function widget( $args, $instance ) {
    extract( $args );

    /* Our variables from the widget settings. */
    //$number = $instance['number'];
    $title = $instance['title'];




    // start the wordpress loop!
    //if ($query->have_posts()) : 

    /* Before widget (defined by themes). */
    echo $before_widget;

    /* Display the widget title if one was input (before and after defined by themes). */
    //if ( $title )
    echo $before_title . $title . $after_title;
    ?>



    <div class="search-box">
        <form method="get" id="searchform" action="<?php echo home_url() ; ?>/">
            <input type="text" value="<?php echo esc_html($s, 1); ?>" name="s" id="s" maxlength="33" />
            <input type="image" src="<?php bloginfo('template_directory'); ?>/images/button_search.png" class="button" value=""/>
            <input type="hidden" name="post_type" value="xyz_resources">
        </form>
    </div>



    <?php /* END WHILE AND RESET QUERY */  wp_reset_query();


    //else:

    //echo 'There are no upcoming articles.';

    //endif;

    /* After widget (defined by themes). */
    echo $after_widget;
}

/**
 * Update the widget settings.
 */
function update( $new_instance, $old_instance ) {
    $instance = $old_instance;
    //$instance['number'] = strip_tags( $new_instance['number'] );
    $instance['title'] = strip_tags( $new_instance['title'] );

    return $instance;
}

/**
 * Displays the widget settings controls on the widget panel.
 * Make use of the get_field_id() and get_field_name() function
 * when creating your form elements. This handles the confusing stuff.
 */
function form( $instance ) {

    /* Set up some defa