yea i wouldnt worry too much about it... as for the piston slap its no big deal, i work at gm and they are going through the same thing... since 1997 almost all of their motors 3.1v6 5.7v8 4.8v8 5.3v8 and 6.0v8 have piston slap and no problems from it whatsoever except customer complaints... they tore down a motor with 300k on it and no internal damage and the piston noise was evidentr from 15k up... everyone has made the piston a little smaller for emmissions purposes and they make a little noise due to slight clearance till the veh warms up soooo.... dont fret just yet you should be fine..