My husband and I have a vent like opening in our glass block bathroom window. It is the measurement of four of the glass blocks and looks like it was cemented in when the glass blocks were placed in to make the window. It is realy old and lets in a lot of air even when shut. I was wondering how hard it would be for my husband and I to replace it ourselves to save money. I was thinking I would knock it out, purchase a new vent window, and place it in with spacers and then recement. Any advise would be great. (I even thought about repacing it with just glass blocks because we will be intalling a bathroom fan to vent to the outside for the first time.) What do you think???? THANKS