[jQuery] an ajax load selector function to replace element

[moester]

I kept having to do

$('#content').load(url + " #content");

but ended up having

<div id="content">
    <div id="content">

What i ready wanted was to completely replace the element with
selected content from an ajax load, hence,

$('#content).replace(url);


/**
 * ajax load content and replace self
 * replaced object must have 'id'
 */
jQuery.fn.replace = function( url, params, callback){

        var id = this.get(0).id;
        if (id) url += " #"+id;
        else {alert('replace object must have id!');}

        callback = callback || function(){};
        var self = this;
        $('<div>').load(url, params, function(){
                        self.before($(this).find('#'+id)).remove();
                        callback.apply(this,arguments);
        });
}

Hope someone experienced with jQuery can clean this up or suggest
another way.