How to limit current of an AC signal
First, you say the conductive surface will have insulation over it.  That will limit the current by itself.

If you want to additionally limit current in case this insulation is removed or circumvented somehow, put a resistor in series with the voltage source.  No, it's basically the same as with DC.

You say the highest voltage is 160 Vpp, which is 80 V peak, which is 57 V RMS if the waveshape is a sine.  By Ohms law, 57 V / 500 &micro;A = 114 k&Omega;.  The common value of 120 k&Omega; should be fine.