My truck has an nv4500, mine shifts very smooth. It's not a short throw like a car, but other than some newer 6 speed trucks I drove... it's the smooth shifting trans I ever shifted.

On the fluid, I'd stick with the factory stuff. Amsoil I believe makes a substitute, but to save 4-5 bucks a quart, think I'd pass. Some places offer the factory style stuff in gallons for much cheaper... but never seem to have any on stock.