The ceiling light won't make a scrap of difference to the exposure, and any light from a window is very unlikely to make a difference unless you're either using a long shutter speed or if it's direct sunlight.
Check for yourself, simply by setting up your camera for the flash exposure and then take a test shot without the flash. If there's nothing on the screen then there's no effect on the exposure.
But it's still a good idea to remove ambient light, because ambient light will reduce the effect of the modelling lamps, making it harder to see the depth of the shadows etc.