If you add this code around line 261 above:
Code:
    if ($display_normal_price == 0) {
      // don't show the $0.00
Code:
if ($show_special_price != '' || $show_sale_price != '') {
  $show_special_price = 'Special' . $show_special_price;
  $show_normal_price = 'Reg.' . $show_normal_price;
}
does this come close to what you are trying to accomplish?