Replacing Slideshow with current header

Hi there,

I was wondering if you could help me replace my current header with the Content Slide plugin.

The code in the header is:

<? if ($xs_disable_slider== "true") { ?>
		<? } else { ?>
		<script type="text/javascript" src="<?php bloginfo('template_url');?>/js/jquery.nivo.slider.pack.js"></script>
        <link rel="stylesheet" href="<?php bloginfo("template_url"); ?>/css/nivosliderstyle.css" type="text/css" media="screen" />

And i need to insert the following:
<?php if(function_exists('wp_content_slider')) { wp_content_slider(); } ?>

How can I add this php code, while its still placed at the original place in the header.

To be more clear, the website is :http://www.succesvollenen.nl/

I want the gallery to show up in the gray ‘box’. But everywhere I try to place the php code, it just shows up in the topleft corner of my page.

I hope you guys can help me out,

Thanks in advance,

Michael