Hi Robyn,
Typically, a _TRANS model is useful for time stepped transient analysis. For most typical DC/DC converter macro models, the transient is ONLY good for transient analysis. That is, that to do an AC analsysis to find say, the phase and gain margin, you would need a STEADYSTATE or AVG model. This is because the transient macro model is using simplified switching elements that dont model correctly in AC analysis. An AVG model has been set up for steady state conditions, and the switching elements have been "simplified' into linear transfer elements.
Most of the time pin numbers are mapped to the model's pin numbers, but this depends on who made the model and what specific device configuration or package the model assumes. In most cases you should be able to inspect the .lib file to see what the pin names are and compare them to the the datasheet.
Best regards,
Steve