My dad has been going Cat skiing out at Monashee for the last 3 years. He is a good skier, but for the average person who goes, they don't take you down the pillow lines that Tanner hits. My dad said that if you really ask the guides and they can tell you know what you're doing they may let you drop some smaller cliffs and stuff if you want.
Anyways, to answer your question: you don't have to be a pro skier to go cat skiing, but you have to be comfortable skiing deep snow.