For anyone who decides to edit ANY file by hand, follow this procedure:
1. FIRST, back up (copy) the original file you are going to edit (put the copy in a safe location).
2. Make a few changes, save, then TEST your edit (e.g., start a campaign). If it starts, the edits are likely OK.
3. Edit the file some more (if needed), then TEST.
4. If the campaign will not start, revert to a prior save or revert to the original (which you safely backed up in step 1).
For advanced users (or kamakazi editors): You are likely editing files within the C:\...\Data\world\maps\campaign\imperial_campaign directory. If you want to be "safe", then backup all files and directories in the \Data\world directory. It is about 114 MB for RTW 1.3 (with no BI). If you get into problems, then restore that orininal backup and you will not need to reinstall the game.
Good hunting...