when I get to step five, I click on fields and there is not field named "Image (field_image_cache)"
That field is set up when image support for Ubercart is installed. Looks like you haven't done that yet - the instructions you're quoting seem to assume that you have image support activated already. There's a brief description how to do this here: http://www.ubercart.org/faq/479
Joined: 11/05/2007