are you doing this in your driveway?
tells about removal and installation starting on page 104
http://www.nicoclub.com/FSM/J30/1994_J30/at.pdf
first unbolt the driveshaft in the middle. then drain the transmission. then there are 10 bolts on the trans that mounts it to the engine. the bottom 4 bolts go into the trans and the top 6 bolt to the motor. you also need to disconnect the wiring harness, gear position linkage on inhibitor switch and the 2 oil cooler lines.
i did this with the car on a lift in about 1.5hrs. ive also dropped manual trans on 300zx which are similar in same amount of time in the parking lot or in my friends garage just on jack stands.
i had a few friends there the night i removed mine cause i wasnt putting the auto back in lol
