The key to a weatherproof, attractive glass block window both inside and out is to encase it in a custom-built wooden frame (Fig. A) with inside dimensions that are 1/2 in. taller and wider than the panel itself. That will give you room to adjust and shim the panel exactly and then inject expanding foam between the frame and the panel to lock it into the opening (Photos 3 and 4).
Turn off the main water supply to the house, and in a convenient location, cut the hot and cold water supply pipes for the bathroom. Also cut out and remove all the existing water lines and fittings in the bathroom. Finally, cut out and remove the vent section leading to the sink and the main stack 5 in. below the vent tee. Stuff rags into open drain lines to keep sewer gas out of the house.