Are you sure the squealing isn't coming from the actual brake pads/rotors? It is a common thing on skylines and I'm sure a search here would bring a heap of threads about it. Does the pedal feel soft...ie you brake at a point and to maintain the same braking force the brake pedal drops more?
Brake bleeders are basically a hand pump (although you can get elec ones)....you disconnect the brake line at the caliper, attach the bleeder to the system and pump the fluid out. You also use it once you are finished to get all the air out the system. Most tool places have them....