jquery change input value with click handler

I am trying to change the text in the submit button on click. Trying to stop multiple submitters.
I have this in header.php:

<script type="text/javascript">
$("form.buttontext")
.submit(function() {
var $form = $(this);
$.post($form.attr('action'), function(){
var $submit = $form.find("input:submit").val('Processing');
window.setTimeout(function() {
$submit.val('Register Now');
}, 5000);
});
return false; //
});
</script>

also tried disabling submit on click:

$('input:submit').click(function(){
	$('input:submit').attr("disabled", true);
});

Also tried this:

$(document).ready(function(){
                $('#gform_submit_button_6').click(function(){
                $('input:submit').attr("disabled", true);
                });
        });

Can someone please shed some light on where I am going wrong? I cannot get a click handler to work. I tried the submit handler too. No luck. I am obviously new to this and trying to learn!