I am planing to put three LED's in my N64 controller.
One in each of the handles. I have never done anything to an N64.
I need to know where I would hook up my wires to get power to the LED's, BUT...not use too much current to where the controller no longer controls the actions on the game.
connect the LEDs up to the 3.3V line look for controller pinouts to find which pin this is. You are going to need a current limiting resistor in there. To find out which resistor I refer you to This page on LEDs
Basically you need to use the equation halfway down the page (Vs-Vl)/I = R. So if you have a standard red LED that is 3.3-2/0.02=1.3/0.02 = 65. Therefore you are going to need a 65 ohm resistor for one LED. It probably won't die if you connect it up without one especially if the LEDs are in series.