You can make a full backup using Windows Explorer, than delete all except the map folder.
Download this copy of the 9.450 Navcore
[Please Register or Login to download file] Unpack the content to the root of your device.
Disconnect and start your device, after a short moment you should be promted to set your device.
If all is working fine you can seek for the latest available map for the region you seek, 890 is current but not all maps are available at this time.
Use the 885map or your current map unil the 890 map for your region is available.
The Navcore has support for the asian language and the asian computer voices.
But I have no download links for the vocies, you might check yourself if you find them as I can't read in the asian forums.
You might have to update your bootloader if it is below 5.5120