Noise source in orcad pspice
You can simply simulate the noise source as an ac source. For ac analysis, you're only looking at the small-signal effects from a single frequency component of any signal (noise or intentional) anyway.


  all my voltages would have a crest factor of 5


Crest factor is a way of describing how your signals are shaped if they are not sinusoidal. It doesn't have any importance in an ac analysis of noise behavior.