Judy, Hi, and welcome to 3FC! This is a wonderful group who offers such great support. We're glad to have you.
I don't know about the "Week 1" book because I don't go to WW meetings. But the best way to know what is core and what isn't is the Complete Food Companion, which I'm sure you can buy at meetings. I ordered mine from ebay. It tells you what things are core/non-core and how many points to count for each item. The products are listed by brand, etc. so you can get pretty specific. You are right about the baked potato/corn scenario though.
I've got to run because I'm at work, but I'm sure the other ladies will be along soon to clarify. Most of them know a lot more than me!
Welcome!