Ok, at least you are trying to do the right things, so props for you!
A few basics:
1. Water does not host much (if any) of the nitrifying bacteria (the beneficial bacteria that converts ammonia to nitrItes to nitrAtes). This bacteria lives in the substrate, rocks, filter media and other places).
2. You may want to consider getting rid of the CC substrate, it is difficult to keep clean, gets all kinds of gunk in it and can limit your clean up crew.
3. PWCs are your best friend at this point, to at least keep the ammonia down.
4. Your corals may be toast and generally need a more mature tank. The first 3-6 months, your tank will go through many changes until it "settles" down.
5. PWCs are your friend right now...or did I already say that? LOL!.
Just keep up the work and see if you can at least take the corals back, if not, you may want to find another store that will.
6. We are here to give FREE advice, your LFS
is in it to make money (as you can see, they pulled one over on you).
Just keep us updated and we will do our best to get you up and running.
Remember, we all probably had the same questions you will be asking in the near future, so ask away!