Re: how much rust is too much for inside your gas tank?
If it was really nasty I would ask for a replacement. Some crust and rust is normal, and treatable. Get out as much as you can, then put a bunch of clean screws, nuts, BB's, chain, etc in the tank and shake the heck out of it. This gets most of the crusty stuff. Then spray with PB Blaster or Kroil a few times, double rinse with premix gasoline and you should be good to go.