I suggest taking a look at 5 Tips for using jQuery with WordPress. Among other things, it shows the code necessary to load jQuery frofrom Google's library:
function my_init() {
if (!is_admin()) {
// comment out the next two lines to load the local copy of jQuery
wp_deregister_script('jquery');
wp_register_script('jquery', 'http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js', false, '1.3.2');
wp_enqueue_script('jquery');
}
}
add_action('init', 'my_init');
You could also check out the Use Google Libraries plugin.