Yes you can edit those files manually with a hex editor. The formats are in Rebellion Editing thread.
You may be missing a dll required for the RebEd to run??
There is another editor to try, it was made a few years ago. It is called SWR editor. I have a copy.
Erratone made it. SWRdataEditor
http://uploaded.to/file/rpa9fhA copy of it. My ISP connection has been fried for a week now...barely able to get here. See if that works on your computer.