Dashboard light and radio flickering

This sounds like a potential ground issue. Looking through the wiring diagrams, it appears that both the headlamp switch and radio share the same ground (W15/5). Attached are screen shots of this ground. It's located in the left foot-well area. Typically, this is the area located just to the left of your feet when seated in the vehicle. There is a plastic trim panel covering this area that will need to be removed for inspection. It's typically held in place with push pins/clips. Once that's out of the way, you'll see a point where several black wires come together and are joined in an eyelet which is secured to the body with a bolt. It will look something to what's in the attached picture. Make sure the ground is clean(no corrosion) and tight.

Let us know what you find!