thanks, that gives me the confidence to get this done then. I am hoping the breaker trips only b/c of a gasket leak and not a casing leak. I have seen videos on changing the casing with folks saying you can do it under water and some say you have to remove the water to change the casing b/c you have to apply silicone where the wire comes out into the niche.
Does anyone want to place there opinion or state fact about whether or not you can pull wire and replace the casing while the pool is full (of course I will only be doing this if the casing is leaking and causing my ground fault)?
You don't need to apply any silicon unless there is something wrong with your conduit feeding the light. Changing the light is fairly easy if your conduit is okay.
Here's how I'd suggest going about it:
Shut off the breaker for the light
Pull the light and put it on the deck.
Disconnect the wiring at the junction box.
Try pulling the old light cable back and forth in the conduit to see if it moves freely.
If the cable moves, cut the cable near the light. If the cable doesn't move, you may find it very difficult to proceed.
*If you are extra careful like me, you might want to temporarily wire the new light into the junction box and power it up briefly to verify it works. If you can't switch it on and off quickly, put it in the water for cooling.
Tape the end of the new cable to the pool end of the old cable. Really, really well.
Pull the old cable out from the junction box end, which will pull the new cable in.
Mount the new light in the niche.
Wire to the junction box.
Verify it still works.