Unfortunately this is not as straight forward as changing a few bulbs. Each 'lamp' in your projector is actually a fully functioning picture tube or cathode ray tube with it's own scanning coils, driver circuit board and EHT (1000's of volts) supply attached.
Once the three tubes are successfully replaced you would then have to re-allign the picture geometry on each of the three images to correct for convergeance errors between the red green and blue elements of the picture respectively.
Good luck in finding the replacement tubes.
Kind regards
Chris
Chris Topping
May 2006