I just had the same problem with my Datsun. I didn't notice the fluid being low enough to get air in it, but I guess it did anyway.

Found mine by following the line from the master cylinder under the car, then just looked for the transmission and the lines that go near it. Looked for the part that looks like the shiny new ones on the online store sites, and well...bled it as best I could on my own.

Sat in my front yard for 2 months, and all it needed was bled.