googlecheckout help needed

[BlushFashions]

I am busy installing googlecheckout as we speak.I have come to the bit where i have to manually alter the code.Now before I do this can I check with someone that will not mess everything up and remove paypal?I want to use both not replace.

[BlushFashions]

Also I am asked to drop a file in to replace one alreadty there
tpl_shopping_cart_default.php
But how exactly will this affect things?

[BlushFashions]

ok I think I am talking to myself here but never mind.I have just compared the two files I mentioned.Not too certain about somethings.Certain bits seem to have been omitted which are in the original but not sure why?
Still no further with the manual code it asks you to replace