Re: @Rob
Sorry it was Android Authority I got the other article from:
http://www.androidauthority.com/how-to-replace-cracked-nexus-7-screen-209240/
My memory was clearly shot yesterday as it was eBay I got the unit from not Amazon, it was from a user called 'weloveaccess', they have good standing on eBay and they have more stock by the looks of it, the unit comes with some tools for prying.
The trickiest bit I found was removing the silver plastic surround from the unit, a hair-dryer is definitely recommended to loosen the glue, if any gets stuck to the screen don't worry it is possible to peel it off and re-apply it to the plastic surround so you can stick it to the new unit. Almost forgot, have a pair of tweezers on standby as well ;-)