Well I wasn't all that brave. When I did it the second time, I just opted to push number "3" which just exited.
And for mine, it just reflashed the 1.0.4 upgrade. I don't know of a way to get back to 1.0. But for me, the 1.0.4 upgrade is working fine and my Kindle stopped being so buggy. There are others that upgraded and never had a problem so then didn't have to reflash at all. Luck of the draw I suppose.
