Hello fello Michigander,
To replace the switch boot from the tailcap, you'll need a tool with fine or pointed tips that will fit the tiny holes straddling the battery contact such as tweezers, scissors, or maybe mini needle-nose pliers, but strong enough to tolerate a bit of torque. Place the tips of your tool into the holes and rotate counter-clockwise until the entire switch assembly can be removed. Then remove the metal washer at the bottom along with the rubber switch boot which can pushed out from the exterior. Make the exchange, reverse the sequence and your done. Be sure to re-tighten the switch firmly before you replace the tailcap to the light. Enjoy!
All the best,
John