In theory, yes, plug and play is just that. However, a sound decoder needs more wires, and some plug-ins are less user friendly than others. Open it up and have a look before you purchase anything. Make sure that the sound decoder you want to install has the same number of pins as the socket on the loco.
Connecticut Valley Railroad -- A Branch of the New York, New Haven, And Hartford
"We don't stop playing because we grow old. We grow old because we stop playing." --George Bernard Shaw