Hey BEC,
Reading through this post, I think the answers so far have been very adequate. Still, (perhaps I simply missed it?), I think we need to focus just a bit more on the character of God.
God is, first and foremost, Holy. In other words, He is totally and completely without sin, so much so, in fact, that sin is defined as that which goes against the nature of God. As K pointed out, when we say "God is good," we often do not realize the depth of that statement. I have often thought that it is better said, "Good is what God is." I hope that subtle difference is clear enough.
Now, under this idea, then we see, along with Lewis, that God is either "the great safety net" or "the great terror." Try to imagine perfect goodness. Before it, you would be completely and utterly exposed. For the first time, perhaps, you would see just how "now good" you really are!
The problem here is that God cannot permanently associate Himself with sin. Again, this has been pointed out--in doing so He would be, in a true sense, going against Himself. He would no longer be separate from sin (being, now, in everlasting relationship to it), and as such, He would render Himself unholy. However, an unholy God is not God, so we have a problem on our hands: above us is a perfect God, and precisely because of that perfection, we cannot be in relationship with Him.
Enter salvation: the obvious result of the above situation is separation from God. If, then, there is any hope to be in any kind of positive relationship with Him, then we must be perfected. We cannot do it ourselves. He must. At this point, it gets complicated, but it can be condensed as follows:
1) God is life.
2) Death is separation from life.
3) Thus, death is separation from God.
4) Imperfection (sin) must be separated from God.
5) Thus, sin must suffer death.
6) Jesus Christ died, though He never sinned.
7) Thus, God may consider sin dead in Christ.
Thus, God may consider our sins dead in Christ.
9) Jesus Christ was resurrected from the dead.
10) Thus, for those whose sins are dead in Christ (that is, they "die in Christ"), they may rise with Him eternally glorified.
11) In this perfection, they may be in perfect, eternal relationship with God.
There is a lot going on in the above, and each statement could support pages of explanation, but I hope that each is simple enough that you can see the procession of thought. Someone has to die for your sins. The question is, who will it be? If you die, then, you pay your own penalty. You are separated from God. God, because He loves you, allowed His Son to be separated from Him. In this way, God may
choose to consider your sin dead in His Son, so that in His Son's death you die, but also in His Son's resurrection you live.
Anyway, that's my two cents worth. If you are interested in the subject enough to continue persuing it, I'd recommend going to any good library or Christian bookstore and either picking up a book specifically on the doctrine of salvtion ("soteriology," to use the technical term), or a basic work on systematic theology. Charles Ryrie has a good one entitles
Basic Theology. In all such books there are sections pertaining to the saving work of Christ.
God bless
note: my browser is blocking pop-ups, so at the moment, I can't run the spell check. Sorry in advance for anything missed.