If the car has ever been painted, its a good bet that the antenna isnt grounded correctly. Check where the antenna meets the bottom of the fender for a good ground. Tune the radio to a strong AM station. If you cant pick up AM, more than likely your antenna is shot and needs replaced. If you can, it may be the radio. You have to realize you are dealing with 25+ year old technology.
On the crackling noise, 20 year old speakers are probably shot, even its just one, it may make the head unit wig out and not supply proper voltage to the rest of the speakers. I'd start there. If you need any further assistance, lemme know. Good luck...
-There are 10 kinds of people. Those who understand binary, and those who do not.
-If we ever forget that we are One Nation Under God, then we will be a nation gone under...Ronald Reagan