Unfortunately, the game files are very unforgiving when it comes to errors. My first attempts were disasters that involved reverting to my back ups over and over again.

Keep at it. Modding isn't as easy as BKB and VikingHorde make it out to be. Go slow and change a little at a time. Make sure you double and triple check your work, letter by letter if you have to. It gets easier the more you work on it.