a tranny swap is not that hard to do if you have a good donor. youll have to install the manual style bracket that has the clutch pedal linkage attached to it.... here, try this thread, this guy is doing the auto to manual swap and has included pics as well...
http://www.nissantalk.com/forum/show...threadid=93767
go ahead and join the site while youre there too, youll be happy you did.