[jQuery] Replacing elements when validate successful

[LVR]

I'm using the 'Validate' plugin for simple form validation - using
'highlight' and 'unhighlight'.  That part is working (though sometimes
the label elements disappear totally - but that's another issue).
What I'm trying to accomplish is this:  When the form is valid, I want
to replace the submit button with an animated gif while the form is
submitting.  From what I've read, I need a submitHandler.  I'm a
novice at js and even more so with jQuery.  Can anyone tell me what's
wrong with this code?

$(document).ready(function(){

$("#register").validate({

    highlight: function(element, errorClass) {
        $(element).addClass(errorClass);
        $(element.form).find("label[for=" + element.id +
"]").addClass(errorClass);
        },
    unhighlight: function(element, errorClass) {
        $(element).removeClass(errorClass);
        $(element.form).find("label[for=" + element.id +
"]").removeClass(errorClass);
        }
});

$("#register").validate({
    submitHandler: function(form) {
        $('#SubmitFormBtn').style.display = 'none';
        $('#PleaseWait').style.display = 'inline';
        form.submit();
        }
});

});

Thanks!
...LV