According to the factory service manual (available at
www.nicoclub.com/FSM/ ), the model is either RS5F32A or RS5F32V. I think the A and V refer to if it's an LSD differential. From a quick google search, I'm seeing this transmission mentioned in pages mentioning the NX, Pulsar, & Sentra. When I check
http://www.car-part.com it only brings up G20s, so there may be some difference. I think I would try to just get one out of a G. Check out
http://www.car-part.com and you might be able to find one in a local yard.
Heath