WARNING: This page is about a different car, the 2003 Subaru Outback, 2003 Subaru Legacy, and 2003 Subaru Baja. 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.