The best place to start if you need help with a specific product is to contact the developer. All WHMCS Marketplace developers have both a website and support URL listed.
Switch language, currency and your client area template basing on a customer's location.
Greek language file for client area
Automatically detects a visitor's location by IP and sets the language and/or currency you defined for his particular country.
Fully supported Automatic Currency Selection WHMCS! The customers currency is detected automatically during their first order and set, so they always get to pay in their own currency!
Here you get a German translation of all WHMCS E-Mail Templates