Robert, I looked at the circuit and there is a simple jumper you can do to get the tractor started if you want. The glow plug TIMER just supplies a ground to the coil of the glow plug POWER relay. With the plug removed from the TIMER, jumper pin 3 to pin 6 in the plug and you'll get glow plugs ON. Hold this for 5 or 6 seconds, remove jumper, and then quickly hit the ignition switch and I'll bet it will fire right off. This is a low current circuit, so a tiny little jumper wire will work fine.
Edit: If you look into the back of the plug, pins 3 and 6 are the pins where the black and brown wires attach. The orange and white wires are power to the timer.