I have a 2000 with limited slip...there is a sticker on the inside of the glove compartment door stating some warning about not putting the vehicle in drive with only one rear wheel jacked off the ground.
Also, there should be a metal tag on the diff housing indicating limited slip additive, if you have this tag, you have limited slip.
Then there is the spin test described in other threads on this forum...basically, chock the front wheels, jack up the rear (both sides off the ground), put tranny and xfer case in neutral. Then spin on rear wheel by hand...if it is hard to turn and the other wheel turns same direction, then it is limited slip. If other wheel turns opposite direction, then it is not or your limited slip is shot...or something like that...