Im a bit paranoid about getting live rock from a system that had fish in it. If any parasitic infestation is present then you just introduced a vector into your system. The live sand would worry me even more if there were fish in the system. If I trusted the shop very much then I suppose my fears would be assuaged .
I do wish to qualify my statements as coming from a newbie to sw keeping. Im a bit paranoid from my first few months of the experiance battling ich and or velvet.