radio hum grounding feedback problem dash removel

hi. I have a 1986 olds toronado. it is a base model with no voice alerts no touch screen computer. it has a radio and a factory tape deck mounted below on the center council. I have a feedback noise coming from the speakers when the radio and tape deck are on only when the car is running. I cant even remove the dask trim because all my electromnics are wired to it. how do I disconnect those connectors and will a new radio with the ground wire grounded attached directly to the firewall fix the problem? or can I fix the problem with out buying an aftermarket cd player? thank you oh yeah. all my seat functions work but down. how do I do a quick fix and just get the seat down. once it's there it doesn't ever have to work again. thanks again