i would see about taking them back to the lfs and making sure your tank is cycled before adding fish.
I totally agree, ask your LFS to take him back for a while. Do you have live rock and/or live sand in the tank? Having these items will help your tank cycle. I know it seems like you have to wait for ever in the beginning to add fish, but I promise, in your own interest and the interest of your sea-life, it is a great benefit. One of the best, IMO threads on this forum is the "what I wish I had known first". This is an addicting and rewarding hobby.
Take everything your LFS says with a grain of salt, understanding that they are in it to make money. People are great here for learning new things, and always willing to provide answers when you need them.
Let us know how it goes, You need to have the ammonia and trites at zero, then wait a while checking water levels to make sure that tank has completely cycled before adding anything else. Good luck! We have all been there, trust me.