ngg2.0 Function not found error

I have an image slider in my theme that loads data from a ngg gallery using the nggShowGallery. When i updated to 2.0 the whole site failed with a fatal php error of function not found.

I am aware that this is a theme problem, rather than a ngg plugin problem, but i was wondering if you could give me the new api commands to achieve something similar?

here is the code of the section in question:

<div id="mainslideshow">
<?php
	$field=get_field('slider_gallery');
	echo nggShowGallery( $field[0]["ngg_id"], $template = 'mainslideshow');
?>
</div>

Thanks

http://wordpress.org/plugins/nextgen-gallery/