1)
Jailbreak:
https://wiki.mobileread.com/wiki/Kind....tar.gz_method
2)
Removing ads:
https://www.mobileread.com/forums/sho...d.php?t=175512
3)
No, Windows explorer won't do. In case it bricks, you need to get your hands dirty. See the Wiki page, and the sticky thread in the developers' corner forum. Up to you to decide.
Generally, if you're only using the device (i.e. if you only used tested and verified methods to modify your device), and don't poke around a lot in the system internals by yourself, the risk of a real FUBAR brick is low. And even then, there is always a remedy.