magento invoice edit text

I am trying to to edit the text that appears in the invoice.ex: to change tax to deposite or grand total to total due.Anyhow I don't want to change the amount of tax.I have tried searching on it a lot.I have I tried to make some changes in the mage/sales/model/order/invoice.php and mage/tax/block/sales/order/tax.php.I have also tried to change other mage files but of no use.I am a newbie please help. any help will b开发者_Python百科e appreciated.

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Use either inline translation or locale translation.

The former is good for a quick change that only applies to the current install of Magento. The latter is better when you want to distribute your changes with extensions or themes to other sites.