These electrical interferences are usually very difficult to locate but they usually come always from the same places...
Did you always hear this noise before? Or this was the first time?
Tings that can make such interferences are GSM phone installations and a bad (don't know the name in english) the element that recharges the battery and gives electricity to the car when the engine is running.
Another possibility is that as you are telling me, many lights on your head unit are dead. Maybe the head unit suffered of a short circuit and the electrical noise reducer in the unit died as it is not normal that lights die in a head unit (unless it is 25 years old...).
As for head unit replacement, the choice is big. First of all you need to choose what type of music you like to listen to. Then the style (look) of the device, the options you can get (cd changer, minidisc changer...)
I would suggest you, if you are listening to Techno and other electrical music to go for a Pioneer or Clarion head unit. If you want to listen to country, classic and other type of music, go for an Alpine head unit (best but expensive).
Whatever head unit you choose, I would suggest you to get it with a tape player and have a cd or minidisc changer in the trunk.
Hope this helps

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