nooooooooooooooooooooooooooooooo
at least you might have a spare tranny thats good, I think the ecu handles the gearing and stuff. have you checked the harness of the ecu at all? might be worth trying a replacement ecu...
FIRST call though, take it to a place that knows nissan and can do some proper troubleshooting on the software side. Think you need to pare the ecu with the car otherwise you could ask anyone with an autobox to lend theirs. feel for you mate