I'm currently working on upgrading a product for the Chinese market. The target is a ARMTDMI7 with a QVGA display. Most resources I've located on the net are targeted at desktop or web programming rather than embedded devices.
There are many ARM microcontroller forums which will help you find what you're looking for.
Atmel has a line of ARM7 processors, and they are pretty friendly to those who make a hobby out of this, so there's a lot of information on this processor. It won't be the same, but generally the tools and libraries can be used across the ARM line so you might find some help here - you'll want to focus on the AT91SAM7 series.
If you have more specific questions, you will probably get some reasonable response here.
It sounds like you need to upgrade an existing codebase to make it support multiple languages.
If so, the fact that this is on a microcontroller shouldn't be an issue - I'd drop that fromt he title and focus on the language you're using (c?) and ask how to convert your program for internationalisation.
This is a problem many people have solved on a variety of platforms, and the fact this you're on a microcontroller doesn't mean that the same tools and such don't apply - the relevant factor is the language you're using
I suggest looking at EasyGUI but that depends on what graphics controller you use.
EasyGUI is a tool that simplifies design of user interfaces and comes with complete source code and driver for a varity of display controllers.
For localization you can use EasyTranslate that gives the translater a graphical representation of the interface. This lets the translator see how the translated texts fit on the screen.
EasyGUI is available with unicode support aswell as right to left script.