@ddljohn-- I had a barium enema recently for a floroscopy. There was some discomfort but it was definitely not as difficult as I had thought.
I had to take a laxative and use a saline enema before I was given the barium enema. The barium enema is quite a lot because it has to fill and expand the colon fully for the pictures to come out right. This was the main discomfort, the feeling of fullness in my bowels. But after the pictures were taken, everything else was a breeze.
I was told to use laxatives and enemas for a few days after the procedure though because a barium enema is known for causing constipation. I don't think you have anything to worry about. Just follow all of your doctor's directions, especially about the preparation.