The file you need to make edits is this:
ROOT/templates/<yourjoomlatemplate>/html/com_virtuemart/productdetails/default.php
(default.php or flexv2.php, depends on which one you are using)
And the HTML lines that generates those SHARE buttons:
Addthis:
<!-- AddThis Button BEGIN -->
<div class="addthis_toolbox addthis_default_style ">
<a class="addthis_button_preferred_1"></a>
<a class="addthis_button_preferred_2"></a>
<a class="addthis_button_compact"></a>
</div>
<s cript type="text/javascript" src="http://s7.addthis.com/js/250/addthis_widget.js#pubid=xa-4f734d3509f75765"></s cript>
And the facebook LIKE button is here:
<iframe src="//www.facebook.com/plugins/like.php?href=<?php $uri = & JFactory::getURI();
echo $live_site= $uri->toString( array('scheme', 'host', 'port', 'path'));?>&send=false&layout=standard&width=40&show_faces=false&action=like&colorscheme=light&font&height=35&appId=115329165206253" scrolling="no" frameborder="0" style="border:none; overflow:hidden; max-width:100%;height:29px;" allowTransparency="true"></iframe>
Cheers.