I have a JL Audio 500/1 sub amp that just quit working on me a few years ago, it powers on, but it has no signal going through it. Has anyone ever had one repaired through either JL or an independent repair shop? What would I be looking at price wise? Any suggestions would be great

Another question, anyone know where I can get replacement knobs for the factory radio in my 04 Impala? The volume and tune button/knobs. The paint has chipped all the way off.