Unscrew the old vent by removing the four screws that hold the vent's garnish to the ceiling. The garnish is the cosmetic ring around the vent's opening, found in the interior of the trailer. Pry the garnish from the ceiling with your putty knife; remove it. Use the ladder to climb to the trailer's roof; take your putty and utility knife, micro-adhesive sealing tape, screw gun and new vent. Dig out the caulking that covers the mounting screws around your vent using the putty knife. Remove the screws with your screw gun after the heads are exposed.
Remove the old vent and its residue. Score the caulking sealant around the perimeter of the vent flange with your utility knife; be careful to avoid cutting through the roof. Wedge your putty knife under the flange. Slide it around the perimeter of the vent to break it free from the roof. Pull off the vent assembly and set it aside. Scrape off any caulking around the vent opening with your putty knife.
Apply micro-adhesive sealing tape around the new vent flange. Square off the corners of your vent opening with the jig saw if the old vent has rounded corners and the new vent is square. Cut strips of micro-adhesive sealing tape with your utility knife to fit the sides of your new vent's flange. Apply the tape to the bottom of the flange. Press the new vent into the vent opening. Press hard enough that the tape bonds to the opening.
Screw down the vent, and place micro-adhesive sealing tape around the vent perimeter. Reinstall the mounting screws through their holes in the vent flange. Cut more strips of micro-adhesive sealing tape with your utility knife to go around the perimeter of the vent flange. Cover the screw heads and the edges of the flange with the tape. Press down firmly to ensure a good seal.
Reinstall the garnish trim. Remove your tools and the old vent from the roof, and go back inside the trailer. Press the garnish from your new vent into the vent opening in the ceiling. Use your screw gun to reinstall its four mounting screws.
