EndfMysteries, I'd like to address two of your questions.
The first is this business about radioactive decay. Jgnat said that elements are elements forever, and that is not strictly correct, as Jgnat's illustration shows, the radioactive isotope Carbon-14 turns into Nitrogen-14 and two sub-atomic particles when it breaks down. So, if you have an old sample of Calcium Carbonate - CaCO3 - and you do an analysis of it and find some Nitrogen (N) in there, the Nitrogen had to come from somewhere - from the decay of Carbon-14 into Nitrogen-14, which is a stable non-decaying form of Nitrogen.
To this question, "It's also claimed the oldest rock/elements found on the Earth are 4.5 billion years old, so that is how old the Earth is. Does that mean that out of thin air the Earth appeared? What if those rocks and elements were floating in space from 4.5 billion years ago yet they clustered and gathered and formed the Earth only 1 billion or 1 million years ago? Is there more to the dating techique that specifies when they became part of the Earth?" I would offer:
First (more than 13 BILLION years ago) there was the Big Bang, then energy began to become matter - individual atoms. The atoms bumped into each other, sometimes becoming compounds, sometimes becoming dust bunnies. Bunches and bunches of dust bunnies bumped into each other and the dust bunnies became large enough so that their combined mass gave them some significant gravity, and so the rate of collisions with other dust bunnis began to pick up speed. As the mass grew, so did the gravity of the mass. Now the dust bunnies were becoming rocks. As these clouds of rocky particles came crashing into each other, they got hot. VERY hot. The heat allowed a couple of things to happen - the bits of rock were now blobs of liquid rock, and because the mass was liquid, elements of different densities separated. If we had a very old rock in which some of the potassium had decayed into argon, the argon, being a gas, could now boil off of the hot molten blob.
This had the effect of resetting the atomic decay clock. Once the molten blob cooled off, it containrd none of the argon it had before it melted. So when we measure the amount of argon in a rock that contains potassium, we know that when the rock was molten it had no argon in it, so all the argon we find must have accumulated after the molten blob cooled off. Thus we can calculate how long the rock has been solid. This is the age of the rock.
Many of the 90 naturally occuring elements have radioactive isotopes, and these elements decay at different rates. This gives us ways of measuring different lengths of time.
You said, "...I'm back in college now, in the fall I'll probably be fullfilling the GE requirement for physical science, I may or may not chose physics for that."
I don't know what "fullfilling the GE requirement" means.
Your intentions are good, but don't expect CHEM101 or PHY101 to answer all the questions you might ask. Become a science major (HARD WORK!) and study chemistry, physics, nuclear chemistry and LOTS of math.