Wow.
You may have problems running two devices off the same sensor - the sensor varies resistance based on temperature, but I don't know how well either device deals with doubling the impedance. Cliff notes: try it and see if they both still work.
As far as wiring up a standard Bosch-style relay - it has 4 (or 5, don't worry about pin 87a) pins on the bottom, that are labelled:
85/86 - these are the "coil" that get the "signal" to turn on the other pins - wire one of these to +12v and the other to your fan controller.
87/30 - these are the "power" pins, so wire one to fused +12v and the other to your fan's red wire. Black wire on the fan goes to a good ground location.
If you want to be cool, wire the "coil" +12v to the same +12v you use for 87/30. Keeps wires running to the relay at a minimum.
That's it buddy
Enjoy your doodads.