WARNING: This page is about a different car, the 2002 Subaru Outback and 2002 Subaru Legacy. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect ground cable from battery.
Remove lens (A) and room light mounting screws (B).
Fig 1: Removing Lens & Room Light Mounting Screws
Courtesy of SUBARU OF AMERICA, INC.
Disconnect harness connectors and remove the light.