Are you going to be using a flash? If so, no worries on the settings as the flash is your lighting and the camera will probably do fine at standard settings.
If not using flash, I'd probably recommend using a middle ISO, 400-800, and closing down the aperture to the F8-14 range...if you intend to shoot handheld...so you can still keep shutter speeds of at least 1/50 or so. If you're going to be tripod-mounted, then lower the ISO and go with longer shutters - but keep the apertures smaller. Either way, I'd think you want a smaller aperture to increase the depth of field in shooting wide shots of rooms. Also, I like to try to shoot interiors opposite the sun, rather than into it - even if it requires shooting one half of the house early and the other half late...especially with scenes where you might want to include the view, it helps to have scenery outside the window instead of blown-out light.
