installing a dimmer switch / replacing the original on/off switch - I have done this before in regular home, and normally when you take off the old switch, you find a metal box in the wall with small wires coming out. You simply attach the new switch to the small wires. But when I took off the old switch (modular home) I found it attached directly to the thick wiring in the wall instead of routed through a metal box with smaller wires going to the switch. Can I install the dimmer directly to this thick 'wall wiring?