This should usually be done by a contractor who understands how the window will come apart. The sash (the body that retains the panes) is removed and is also then disassembled as a way to go ahead and take IGU out. A completely new replacement IGU (ordered from the window https://superman71977.loginblogin.com/42071231/helping-the-others-realize-the-advantages-of-window-seals