You can modify items through the editor, or by editing stat files directly, but you'll need to extract the files if you want to use the text files. I recommend the editor to start with, though. If you're mod isn't dependent on Origins, you won't see the armor from the main campaign. Extractor:
https://s3.eu-central-1.amazonaws.com/nb-stor/dos/ExportTool/ExportTool-v1.8.2.zip