knockoutking027

So i JUST passed the 100k miles with my 02 S55 and I have had a lot happen. New brakes although needed cost a grip. Service B a waste of $$. Power door locks and door vacuums do not work. At nite when i start the car (when the engine is cold) and my radio is on my instrument cluster dims and brightens to the beat of the music (bad alternator?). Also on the cold starts my HID lights flicker which is not normal. are they not getting enough juice or time to replace? and now when im driving there is a wierd humming noise. If you are standing outside the car you CANNOT hear it. If you pop open the engine compartment you CANNOT hear it. The sound is the loudest INSIDE the car. Along with the sound I can feel the ground under the drivers leg and back left passengers legs sorta vibrate. and it sorta sounds like i have a supercharger on the car but it can only be heard from inside the car.

So I was wondering . . . do i need a new alternator ? new hids, cost? and wtf is the whining noise?

Any help is appreciated thanks.