CrossRoads:
Yes, you need the diode. When you stop the current flow in the delay coil, the physics of the coil will try to keep the current flowing, creating a nasty spike of voltage. The diode dissipates that spike within the coil.
The TIP120 will work to drive the relay. Use a resistor of around 470 ohm to1K between the arduino pin and the base pin of the transistor.
Oh yeah! Its like when working with a DC Motor, makes sense.
Thanks again. Going out now to get the diodes and hope to try this out this afternoon.