Bosque is a great place, and the advice you got about timing is good. Once the dawn flyout is over, you might check out the pond just north of the entrance to the refuge on the west side of the road. That is also a place that the cranes inhabit and it is right next to the road. Your 400 is more than enough there. The photos of the cranes on my web site were taken at that location. I was using a Sigma 50-500 on a Canon D60. See My Bosque Pix
Late November or early December is, I have heard, better than early November. In either case it will be quite cold in the morning and at dusk, so dress accordingly.