Default [Q] How can I unroot for warranty with unresponsive screen?

Hi guys,

My I9100 has an unresponsive screen and is still under warranty, or would be if it wasn't rooted!

So there's the problem, how can I return to stock, reset the flash counter etc to get it fixed under warranty without using the screen?

I'm running 4.1.2 firmware.

Thanks in advance!

Al.