Morning. I need some help. I have 2 wet niche Swimquip model #05082 12 volt 300 watt lighting fixtures that need replacing. They are over 20 years old. We want to install a replacement LED fixture that will fit the existing housing that is installed into a Gunite pool, problem #1. Problem #2 is the threaded nut that is part of the niche, where the retaining screw of the face ring connects, has corroded off. To the point where I can not reattach the face ring of the housing, back on the niche. I can't be the first one that this has happened too. 

Thank you for the help