How to enqueue jquery in admin and why is it not already there?

Question

First, check for syntax errors. The syntax highlighting seems to indicate that you have syntax errors.

Second, don’t wrap your add_action() calls inside conditionals; rather, wrap your callback function content inside the conditionals, e.g.:

<?php
function theme_upgrade_alernt() {
    if ( is_admin() && $pagenow == 'theme-install.php' && $_GET['tab']=="upload"){
        // CODE GOES HERE
    } else {
        // ELSE CODE GOES HERE
    }
}
add_action('admin_print_scripts', 'theme_upgrade_alert');
?>

I would also recommend enqueueing your scripts at admin_enqueue_scripts, rather than admin_print_scripts.