It's absolutely possible the previous owner shorted out a board trying to power the amp, but it's also possible the cluster died all by itself. I've had it happen. I'd be very surprised if removing the radio will change anything at this point. If that's what caused the problem- the damage is done.
Is your shop equipped to work on clusters? Most independent shops aren't and dealers seem like the only option. I don't subscribe to that kind of reliance so I went looking and Chevrolet Instrument Clusters - Replacement Cluster Panels, Dash Panels, Gauge Clusters, Speedometers for Chevrolet turned out to be super helpful. They literally only deal with clusters, so they know what they're talking about. I got my old bad cluster cloned, mileage and all, avoided the "tampering" pitfalls, and didn't have to pay dealer prices! Definitely would recommend giving them a call, they'll help you figure out if that's where your issue is.
Is your shop equipped to work on clusters? Most independent shops aren't and dealers seem like the only option. I don't subscribe to that kind of reliance so I went looking and Chevrolet Instrument Clusters - Replacement Cluster Panels, Dash Panels, Gauge Clusters, Speedometers for Chevrolet turned out to be super helpful. They literally only deal with clusters, so they know what they're talking about. I got my old bad cluster cloned, mileage and all, avoided the "tampering" pitfalls, and didn't have to pay dealer prices! Definitely would recommend giving them a call, they'll help you figure out if that's where your issue is.
