another thought, you should check your trunk lid whenever you open it, and if you found any condensation on the lid, you must wipe them dry and leave the towel somewhere else. This is mandatory.
Also, when it's wet outside, quite a bit of water can be introduced into the trunk when you open it. so beware of that too.
If you have a garage, then dry your trunk and leave the trunk lip open for couple days should be able to dry up the trunk and lights.
Since your CD Changer is too wet that it won't work anymore, I would say you had the wet trunk problem for quite a while now. I'd also moved the changer out and leave it in house, hoping that the warmer and dryer air in your house would completely dry up the changer's internal. It might work again.