My 1990 GB 32 (#834) has exterior aluminum window frames all around. My starboard-side front sliding window (right by the helm) is cracked and I have looked into what it will take to get it out and replace it. I am pretty sure (but not 100%) that you have to do it from the inside, by removing the lower valance--UGH! The boats with Aluminum window frames are apparently pretty rare, and I have not yet found anyone who has actually replaced a window in one of these boats.
Oldersalt