Paolo your answer may be as simple as disconnecting the battery. That may reset the engine light on your 1996 Monte Carlo. The problem is that the cure may be worse than the illness. Disconnecting the battery may cause the loss of other, more useful computer information. And if the problem that set off the engine light isn't fixed the light will just come back on.
The engine light can indicate some serious problems which should be addressed. Take a trip to the dealer and get a diagnostic to rule out bigger issues.
Good luck!