Since you are using ADS just go to the S-parameters tab simulation and put the S-parameters block simulation in the schematic window, activate noise measurement and you are done, about S-parameters and NF simulation.
Why you need a Spice netlist? Any special reason for that?
About term1 and term 2. Term1 must be defined as 50 Ohm (input impedance of an antenna), Term 2 can be 50 ohm or an input impedance of a mixer, usually a capacitor with a few hundred fF depending on technology.