Not sure why this is so hard to find for Ubercart 2, Drupal 6; but if you were to download the contrib module you get nothing but a Google Merchant Developer field in your settings panel, and no RSS feed what-so-ever.

Instead you need to go to this ubercart thread on google base and download the posting that relates to google base. There are several google base files, and some of them only relate to Ubercart 1, not Ubercart 2. The most recent one, at this time of writing, was the Ubercart Google Base file version 2.2.

Once you have this file, you will need to make some key modifications.

Personally I find that exporting the node->body is a bad idea, as this may have a lot of HTML in it, so either export your own custom CCK field for the desacriptions, or use the teaser and then strip the HTML out of it.

Here is my version of the google_base.module file, which also includes a custom function for removing any and all embed or object tags that may be present in the copy of the teaser.