Display custom widget value in header.php

The Codex is your friend. There’s a the_widget() function for that.

<?php the_widget( 'MY_Widget', $instance, $args ); ?>

Refer to the Codex entry for values for $instance and $args.

$instance = array(
    'title' => 'Some Title here',
    'name' => 'Some Name here',
    'show_info' => true
);

$args = array(
    'before_widget' => '', // Your value here
    'after_widget' => '', // Your value here
    'before_title' => '', // Your value here
    'after_title' => '' // Your value here
)