I bet the radio went bad. I wouldn't spend time trying figure it out. If you goto circuit city and spend 100 bucks they install for free on indash cd players. You will notice a huge difference with any aftermarket head unit.
That's my opinion. I know how it is to be without a radio.
Is there any way to wire in a new radio, so then you can use the on dash volume adjustments, because I've been pondering on getting a Cd-player, but don't want to lose the luxury, I don't have coinholders, so there is a space under the base radio, is there a way to install a cd player under it without too much hassle?