Samsung Firmware Modifying! As i'm working as a mobile software technician, alot of times i need to unpack some odin firmwares to add or remove some files, maybe adding some languages which isn't available in the firmware, then i repack it again so i can flash it with odin, i need to understand Samsung firmware structure, i need to know how exactly the system works, for example: I747 is an US phone, which comes with only 3 languages, if i want to add some other languages to it's firmware, then i need to understand the CSC tree first, so i can edit it and add the desired languages pack, i've been searching around for some tutorials about that but i couldn't find any, i know how to unpack and repack odin files, but as i said, i need to understand the system.
XDA is the go-to site for you


This link at XDA Samsung Firmware Naming Convention would give you an insight into the conventions followed for PDA,CSC and Phone, Region Codes,
Year, Month, Revision codes and other useful references


Depending upon the models you repair, you could search XDA for modem related info including collection of modems for different regions
Guide on repackaging firmware
Samsung Firmware Version Number
Samsung Firmware Code Reference
Editing CSC file
Phone Info Samsung is a great tool to help you with many things related to Samsung phones. Quoting from the developers thread it would help you with




  SAMSUNG SPECIFIC:



Phone Colour (Samsung specific)
CSC Product Code (Samsung specific)
CSC Sales Code (Samsung specific)
Country Region (Samsung specific)
RIL Serial Number (Samsung specific)
PDA Version (Samsung specific)
CSC Version (Samsung specific)
Changelist (Samsung specific)
Country of Origin ★ (Samsung specific)
Phone Manufacturing Date ★ (Samsung specific)
Knox Warranty Void ★ (Samsung specific)



  OTHER INFO:



Manufacturer
Phone Model
Device Name
Product Name
IMEI
Serial No
Bootloader Version
Baseband Version
Kernel Version
Build Number
Build Description
Fingerprint
Build Date
Android Version
Mobile Operator Name/Mobile Network Code
Total RAM, Screen size and resolution, Battery capacity and health