Generally the fan will come on when it gets to the "Dot". If you look carefully at your guage it will have a very tiny speck of paint about an 1/8th - 3/16th below the redline. If yours didn't come on it could be a variety of reasons. First thing would be to hotwire the fan and see if the motor is actually good. First thing I would do is check it by crossing the switch which is located under the right scoop. It has the two wire plug on it. Simply unplug it and jumper the wires over. It will complete the ground circuit that way. It won't make any voltage go to the fan if there is none availalbe though.
I usually tie into those same wires with a switch so i can control when the fan comes on. That way when you turn off the key the fan also turns off. No forgetting to turn it off and run the battery dead. Also, if the wire comes loose it won't short anything out since there is nothing but a ground wire.
With a spin on type filter there are a number of filters you can use. I don't have the list of them but i'm sure someone here does.
Sean Morley