this is something on my list of things to do as well, only i think i have a constant fed to an accessory line somewhere.
dash lights always on, park lights always on, no dim control, and when the headlights are on i can turn the car off but still play the radio lol
but from the sound of things the first thing is to take apart the dash and get a better look at things
when i first bought my jeep i had to replace the windshield frame to stop it from leaking . . but i still need to grind out and prime the floor where the water got bad . . . .