How to handle file uploads in "Site Information"? Customizing "Site Information"

Hi friends,

I am customizing my "Site Information" page via my own module (variousoverrides.module), it serves more like site config page at this point. I added a bunch of text-variables:

		/*
		 * SITE INFORMATION: adding another box for home page text box
		 */	
		$form['homepageConfig']['site_home_page_text_box'] = array(
		   '#type' => 'textarea',
		   '#title' => t('Home page text box'),
		   '#default_value' => variable_get('site_home_page_text_box', ''),
		   '#description' => t('This text will appear on home page only under a main photograph. If text will not fit in a box, a scroll bar will appear.')
		);

I also added file upload, like a splash page image:

		/*
		 * adding picture upload
		 */		
		$form['homepageConfig']['site_home_page_pic'] = array(
		'#type' => 'file',
		'#title' => t('Upload Picture'),
		'#description' => t('photograph (650x323px)'),
	   '#default_value' => variable_get('site_home_page_pic', ''),
		'#required' => FALSE,
		);

The problem is: while text-based items are stored and retrieved automatically, it doesn't work with file uploads. I realise I need to hook to _form_submit to handle file uploads is that correct?

If so, can anyone please hint at how do I hook to that submit? I tried a lot of techniques but I just can't figure out how to do this.

Any help will be appreciated,
Thanks,
Vlad