Position your ladder so that you can reach the window comfortably. Place your razor knife at an angle along the edge of the window to avoid cutting into your mobile home. Use your razor knife to cut the caulking on all four sides of your window. Caulking seals the window from rain and moisture.
Remove the screws from all four sides of the window using a drill. Use your pry bar and pry the flange away from the outside of your home. Use your ladder to reach the top of the window. Pry the flange away from your home. Stand on the ground and loosen the bottom of the window. Pry the flange from the bottom as you did the top. Once all flanges have been removed, the window can be removed from its location.
Inspect the opening where your window was once installed for rotten wood. Replace any rotten wood, and remove the old caulking from the existing window slot. Removing the caulking will ensure a water-tight seal on your new window.
Position the new window so that you can accurately apply the silicon caulking to the back of the window's entire flange. Position the bottom of the window even with the bottom of the window opening, and insert the window into the empty opening on your mobile home.
Place a carpenter's level on the top and side of your window. Level the window with your carpenter's level. Replace the screws in every hole around the window flange, being careful not to over-tighten the screws. Your window will now be secured in place. Apply another layer of silicon caulking around the entire new window.