If it's anything like my '68 Dart, it's just 2 nuts that you have to get with a deep socket on the bottom of the a/c vent assy.
But, the best way to see the vacuum hoses and cables would be to remove the glovebox.
As far as I know, you have to have the "heat/cool" lever in heat AND vacuum to one of the vacuum actuators via the push button controller (not sure which actuator) in order to blow heat into the car.
It sounds like you might not have a vacuum signal to the controller, first place to check would be the hose at the back of the intake manifold.
