If you need to make a repair to a leaky shower-arm, or you simply want to make a change for cosmetic reasons, you can probably make the repair or replacement by yourself. You don't need to be a skilled plumber to remove the shower-arm, and you'll need just a few household tools and a small window of time. If the pipe and hardware are old and corroded, you might need to use a little more elbow grease, and perhaps some lubricating oil, but you will probably be able to remove the arm without hiring a professional.
Turn the water supply off to the shower before you make any repairs. The shutoff valve should be located behind an access panel somewhere in the bathroom, perhaps located on the wall opposite from the shower.
Take a pair of pliers and grip the arm firmly. Keep the grip on the arm while you loosen the nut on the shower-head with a wrench. Turn counterclockwise to loosen the nut.
Dissolve mineral deposits around the nut if the shower-head won't come loose easily. Soak a cloth in white vinegar and wrap it around the nut, then try to loosen the nut again.
Use your hand to unscrew the shower-head and remove it from the arm once the nut is loose.
If the shower head doesn't come loose easily, cover the head with a cloth (to prevent scratching), and use a wrench to turn the shower-head counterclockwise.
Turn the arm counterclockwise, still gripping the shower-arm with the pliers, and remove the arm from the wall.
Use a 16-inch pipe wrench if the shower-arm doesn't come off easily. Grip the arm with the wrench and turn counterclockwise.
Spray the arm with WD-40 If the wrench doesn't work. Leave the lubricant on for 2 hours, and try again with the pliers or the wrench.