find pll

I am verifying a PLL block for which I need to find the phase margin for each process corners. The PLL block consists of he following blocks
PFD, Loop Filter (2nd order RC filter), Charge Pump, VCO and a divide by N block in the feedback.
My concerns
---> Should I perform ac analysis for the whole PLL block or the Loop filter only to find the Phase margin.
---> Should I perform ac or stb analysis for finding phase margin.

Can some body give me the details of the procedure invovled.