Speedometer Repair

[RalphG]

On the 52 Mercury the speedometer and odometer has not worked in close to 50 years. Permanently stuck on 120 mph and 82 something thousand miles. The disconnected cable turns just fine at the top end so I'm wondering if I could/should try getting into the instrument panel to clean and lube the speedometer in hopes that is all it needs. Just removing the dash I can see what appear to be hold down screws all around the perimeter at the back. Would removing these give me access to the odometer/speedometer? Or should I just leave it alone before I do further damage. This photo shows the back side of the panel.