Google Checkout install - duplicate checkout_payment.php file

[ReallyNeedHelp]

Hi, I am a real beginner at this :)

 

I have sucessfully installed the Paypal Express and Moneybookers modules, and now what to install Google checkout. I'm falling the instructions to install from Google's site here:

 

http://code.google.com/p/google-checkout-oscommerce/wiki/Installation_1_5_0

 

I am using the instructions for a previously modified site.

 

It says to install checkout_payment.php, but that file already exists.

 

Has anybody any advice about what I should do? :)

[ReallyNeedHelp]

I realised my error!