There are a bunch of things that can go wrong with the radio, because of the number of modules involved. The radio modules themselves can be sent to
Sierra Electronics, but there is a strong possibility of problems in the wiring between the modules, such as corroded connections, shorted wires, etc.
How to proceed depends upon your trouble-shooting skills. Schematics for the radio wiring are available online from several other forums. My first step would be to open things up and check each connector between the modules. The static on receive of the CB can come from a bad antenna connection, which has several connectors in line. Weak audio in general can be a bad connection with the module that boosts the volume, based upon the road speed.