Change to new default curencie and updating all product prices to new default curencie

[didje3]

Hello, i have question, maybe someone can tell me what to do?

Now i have my countries default curencie Latvian Lats (Ls) in prestashop (1.3.2.3) also all product prices are in this default currencie, but from 01.01.2014 or countries new curencie will be Euro, this means that my prestashop must have default currencie Euro. The problem is, how to change to this new default curencie(Euro) and update the old default curencie based product prices in my online store? Maybe some one have som solution or script change in product.tpl or something else?