Removing the CRT shield will expose you to dangerous voltages and currents.
Those threats can still be present long after power has been disconnected from the 5155.
There is a threat to your body from flying glass fragments, resulting from accidental breakage of the CRT (includes CRT neck).
IBM's yellow warning label on the shield is there for a reason.
Before removing the CRT shield, adequately educate yourself as to the hazards/risks/precautions.