My 1999 Taurus

Hello, I an thinking about buying a friends Ford Taurus 1999 with a 3.0 motor. We put a scan tool on it and it said cylinder 6 misfiring and lean exaust. We are both mechanically illiterate! We managed to changed the spark plugs and wires but still having the same problem and the engine light is still on! What do you think it is? Do you think theres a bad piston? The car seem to idle rough. Do you think its a cracked head? The car starts up fine and the engine light seems to go off and on throughout driving range. Someone told me that it might be that fuel injector on that cylinder but before we go taking a motor apart to put an injector in. We want to make sure that is the problem. Like I said, the scan tool is reading "cylinder 6 misfiring" and "Lean exaust" Please help me! Thanks