Planning to change out the fluid. What do you guys recommend?

royal purple, amsoil.. used amsoil and heard good things about royal purple

For manual transmissions, Redline MT-90 is what most people agree to use.

Basically, anything is good as long as it is GL-4. DO NOT use GL-5 as it eats brass syncros(what we have). I ran Mobil 1 GL-5 for quite a while and never noticed anything bad, but nevertheless, its better to follow directions. MT-90 works out really well for me.

If you have any kind of notching going into gear, I hear that Pennzoil syncromesh works very well for helping older transmissions shift smoother.

If you are auto, I'd just look into whatever Nissan recommends..