I haven't really used the creation kit before other than to open it and take a look around.

I would like to edit the base value/cost of some items like food, weapons/armor, misc items. (I don't like some aspects of the existing economy mods I've seen.)

For example, let's say I want to make a Red Apple worth 10 gold. Can I just select Magic>Potion>FoodApple and change the Potion Value to 10? I'm guessing that will overwrite the original FoodApple Potion Value that the game loads, or would I save it as an esp. and the original would be fine in case I want to go back to vanilla?

Also how does this effect my other mods, like Skyre or Immersive Weapons/Armors if I decided to change weapon values?

Mostly I'm concerned about screwing up my game. Should I backup my game files/saves before I start messing with stats? Or are my changes separate from the original files and I don't have to worry?