Re: Google Product Feed Module
The module adds 2 new fields to products and variants. What you call them it doesn't matter. You can call the UPC field UPC or EAN or whatever other label suits you. It's just a text field to hold some value.
Same for the Vendor/Mnfr field.
The point is to use it as it is ready module.
And yes you can most certainly import these values using csv file. These are not attributes, they are product fields. So you simply use the product import.
You can assign the UPC and the Vendor # to whatever field you want for the feed.