If God is omnipotent, wouldn't it be perfectly plausible if he could bend the rules of logic? He can do anything and that way he could both cease to exist and be eternal and make a rock that he can't lift and still lift it. Logically we can't comprehend it but why should he be unable to do things WE don't understand?
And evil exists because of free will. Man can choose to do what will please god or what will please man. Sometimes it is a tough choice, some times not so much.
Free will was described to me once as being like a river system flowing out of a lake. As it flows it branches into many different streams which also branch out. Every time they branch out it's like making a choice. As a person swimming down the riveria of life, all we can see is that there is a choice, but not where it will take us. We can remember the choices we've made in the past, but this is a new one that we'll have to make. The destination of the choice is already set, as in God already knows where it'll take you if you choose to go left or right. The whole thing is set out, it's just that you have to make that choice. And making the right choice is often much harder than doing the right thing.
Eve wanted to be better than God.
Adam ate the fruit because Eve said it was good.
The lessons we can learn here are:
Ladies, you are awesome, but not THAT awesome. Don't self-improve to the point of damnation to all of humanity.
Dudes, if your ladyfriend asks you to do something that you know ain't right, don't do it. Show her who wears the pants, man!
And, er, snakes. Don't talk to the people. They might listen to you. And then you're forced to crawl on your belly and eat the dust.
I must confess, I'm not specifically opposed to fire and brimstone, however, I think it's place is vastly overstated. Generally, I save fire and brimstone for those that believe it exists. 
Kind of loses it's punch otherwise, ya' know?
