People with screen problems on the
Get Satisfaction Kobo Support Board, which is "official" and staffed by Kobo employees, are reporting that readers returned to them that have manufacturers defects involving the screen are being replaced under warranty but that screens that have been damaged by the user are replaced for $70CAD.
If you don't have a response from Kobo in a few days, go to that board and recap with your ticket number. I have no idea how they handle return of readers from your country.