I have a large, healthy cardboard cactus plant which seems to be in need of repotting. I am afraid to disturb it. What’s the safest way to repot and do I need anything special like soil, etc., etc?
First thing you need is to know if you really need to repot. This article on repotting will tell you a little more: https://www.gardeningknowhow.com/houseplants/hpgen/should-you-repot-your-plant-happy-root-bound-house-plants.htm
While cardboard palms are not listed as among the plants that "like" to be rootbound, I think they might be. I have a couple of them in the same pots for 8 years or more. Here's some more information on growing them: https://www.gardeningknowhow.com/houseplants/cardboard-palm-plants/growing-cardboard-palms.htm
Reasons to repot such a plant would be: so big the container can't support it; so full of roots you can't get water into it; you really want it to grow bigger.
A basic guide to repotting: https://www.gardeningknowhow.com/houseplants/hpgen/learn-more-about-repotting-houseplants.htm
For soil, use cactus or African violet potting soil, mixed half and half with perlite. Gently tease apart the roots so that they can grow into the new soil. And wear long sleeves and heavy gloves -- cardboard palms are prickly.