I'm not sure where to get a screen replacement that will ship to India, but a Google search turned up this on Amazon: http://www.amazon.com/Screen-Digitiz...en+replacement
Also you will need whatever tools are listed in this guide: http://www.ifixit.com/Guide/Nexus+7+...placement/9945
Most devices have the digitizer, front glass, and the screen as one piece. Sometimes you can just replace the glass and not need to replace anything else, but it varies. Either way, you're most likely gonna need a heat gun. lots of patience, and a dust free environment to do it in....otherwise you will end up like a buddy of mine and having to take everything back apart to remove the cat hair that got between the glass and the screen.
Anyways, hope that helps.