Turn off the water to your double-wide trailer at the main water supply. This is usually near the water heater, but in some double-wides, can be under the home, according to Mark Bower, author of "The Manual for Manufactured Home Repair & Upgrade."
Remove the screw from the shower head with a pair of vice grips, and the shower fixture should come off. If no screw is inserted, unscrew the fixture from the water supply line with your hands. If the head is stuck, grip the water supply line with vice grips, then turn the shower head with your hands.
Coat the end of the water supply line with waterproof sealant. The sealant forms a watertight bond with the new fixture.
Line up the threads of the new shower fixture with those on the water supply line. Then twist the fixture into place until tight.
Turn the water back on and test your shower fixture. After testing, flush the toilet to release any air or dirt that settled into your exposed water supply line. Debris can damage shower heads.