change line 250:
$pbook = new pbook_Definition("pbook", 0, "\\$AUD", "", true, 2, 0, "oz", true, 2, 1, 0);
to:
$pbook = new pbook_Definition("pbook", 0, "\$AUD", "", true, 2, 0, "oz", true, 2, 1, 0);
to change the currency code sent to payapl, you will need to edit the code that sends the transaction to them.
if you are using paypal payments pro, the confirm page will have this code:
$PP_PayPro_optional[0][$nextIndex] = "CURRENCY";
$PP_PayPro_optional[1][$nextIndex] = "USD";
change it to:
$PP_PayPro_optional[0][$nextIndex] = "CURRENCY";
$PP_PayPro_optional[1][$nextIndex] = "AUD";
if it is paypal standard, change:
<input type="hidden" name="currency_code" id="currency_code" value="USD" />
to:
<input type="hidden" name="currency_code" id="currency_code" value="USD" />