Did mine a couple of years ago.If i remember correctly You need a form from the traffic police. Fill it in and return your number plate with it and your Turkish log book .i think it cost me 100 lira.They stamp your log book to say it has been scrapped and return it to you..Then i sold my old scooter for spares to a mechanic on the Sanay
Your Turkish needs to be pretty good or get one of those guys that sort number plates and insurance out to do it for you .
But ask the price he charges first.
If you dont do it correctly you will be liable to pay the road tax on it for ever more.
Hope this helps
Sorry i can,t be more specific