There is no clutch in an automatic transmission.
I understand that automatic transmissions have coolant hoses that go up to the radiator, is that was you are saying is leaking, or a clutch line? Because really, you have no clutch if you have an automatic transmission.
anyways, besides that confusing issue, the Idle should have nothing to do with the transmission. It most likely has to do with the MAF. Does the car get any worse if you un-plug the MAF, or does the idle stay the same?
also, Idle is controlled by the IACV (Idle air control valve) on the passenger side of the KA24DE block, just behind the water neck area. If you don't have a FSM (factory service manual) get one.
www.240sxtechdvds.org has a FSM for many different cars, including yours.
You live in Alberta by any chance? if yes, PM me, if no, dont bother.