I did some glass block on my own a long time ago and it was ok, but then I found out it wasn't that expensive to have the block window made up by someone else and then just install that myself. As with everything, it's the labor of having someone come out that costs the big $$$. I've done that several times now and it's woth it. Even some of the big home stores will make up glass block windows. You can get an operating window in the glass block too but they can be a pain also, but not as bad as a normal window. As Carlos said you need either a window or a fan in most areas to stay in code.