To fix your flickering interior lights, I would spray some contact cleaner into the slider switch. Take the entire headlamp switch assembly out of the dash, take the circuit board out of the assembly, and spray the contact cleaner *directly* into the potentiometer. You need to remove the entire assembly from the car because there is a dust shield you need to get the contact cleaner straw under. Work it up and down a few times and that should help too. While you have it out DEFINITELY reflow all the solder points and add solder where it is needed.
1996 Jeep Grand Cherokee Limited Edition 4.0L
3.55 axles, stock pretty much everything, except for a PSC steering gear and fuel injectors