That's what happens when you shop at walmart folks. Seriously though that sucks. You've got way too many fish in a 10g for one, we've already established the un-cycled issue, as well as having tropical fish w/ goldfish.
IMHO 10g tanks are best left for the fish that make the 10g look REALLY big like, small tetras, pygmy cories and white cloud minnows. Anything else, even guppies can't really last long without constant water changes and insane over-filtration. If you wind up losing all your fish I suggest taking it all back and demanding your money back for giving you BS info. You're on the right track comming to this forum and others for help, try your luck again, pre-cycle the tank, then research, research, research and when you've done some more research. Pick out what fish you can keep in a 10g and go from there. It's a little frustrating at first, but the amount of enjoyment you get from your aquarium sometimes outweighs the joy you get from your dog that keeps eating your socks! =)