The easiest way to check is to jack up the rear axle and turn one of the rear tires. If it turns easily and the other tire goes the opposite direction you either don't have it or it is completely worn out. If the tire is difficult to turn or the other wheel turns the same way you have it.
Trak loc, and other clutch type limited slip axles require that you use a limited slip additive to keep the clutches from chattering. You can get it at the dealer or any decent parts store.
For fluid go with a good synthetic in the recommended viscosity.
You will only have Trak Loc in the rear unless someone has added it aftermarket to the front.
2012 Silver Sport S, Silver, 6 speed, soft top, 3.73s, LSD, PCG, Infiniti, deep tint windows, Pro Comp 1028 wheels, 33" Duratracs, Smittybilt bumpers and steps, KC fog lights, Mopar slush mats and fuel door.
Happiness is a belt fed weapon.