Well first off I would go to the Wild Hare Web page and download the Generic instruction manul and any specific manuals or instructions for your plane and read those. As you did not put this plane together it might provide a good reference point as to what Wild Hare had in mind for the building.

As to the batteries you can pretty much put them where you want to so long as you install them correctly. The batteries should be fine up front if monted with some foam. EMF or other forms of interferience doesn't really affect voltage, it just screws with the signal so that shouldn't be a problem. Your receiver weighs almost nothing in the overall scheme of things and should not be a problem mounted where it is. If the plane really is tail heavy I would move the battries as required to get the initial ballance recommened in the on line manual. After that it is pretty much a matter of ballancing the plane for the way you like to fly.