To calibrate one or both screens, press the Menu button, Settings, Sound & Display, then "Tablet screen calibrator"/"Reader screen calibrator".

Rooting an Android device is like running Windows using an Administrator account with full privileges. Once a device is rooted, you can change, delete and install anything. For this reason, manufacturers tend to disable full privilege on their devices so that users don't get themselves into trouble. And since once rooted you can change things in ways that tech support can't anticipate (or then deal with), rooting generally voids the warranty, tech support, and firmware updates.

Having said that, Linux gurus who know what they're doing are just fine rooting their eDGes, and doing so doesn't technically "harm" it.

Given that you're just learning about rooting, I'd say: don't do it