Wal Mart etc. stops for groceries

This is scary for us since it is a major change. This will be our first trip in a full blown motorhome. We have to be in Oregon for our daughters wedding, taking our dog with us, lots of changes from what we are used to on this trip. We will have to use a rental car or shuttle buses from the campgrounds. Whole new experiences. Hopefully everything will work out but this is still the first time we have had our dog with us so we have to make sure that it all works out well for the dog as well. This is going to be a learning experience for all of us on this one!!All advice appreciated!