Judging by the properties of glass and silicone I think the tank would be fine, and of course the lights, stand, probably the skimmer, for sure clean it out good with fresh water and make sure its clean. Ditch teh rocks and sand and start over and I think you should be fine... Go over the tank with lots of fresh water and a brand new non treated scrubbing pad (not too course, but if its glass it shouldn't scratch) and thoroughly clean it out with lots of water. If there is any copper residue it should wash off im sure if enough water is applied, and if not all of it, at least diluted to an undetectible about...
I'd go back to the guy and let him hear it, maybe he will realize that you found out his little secret that he doomed the tank like a moron and he will give you some cash to put towards new rock at least? Sorry to hear about the whole situation, that really sucks man. Good luck and dont give up though. Maybe keep some of the rock for a QT tank for fish only, or like biff suggested a nice FOWLR with some nice angels in it? I dont remember the size of the tank, but if its big enough that would be cool. I crave a tank with some big beautiful angel fish!
