thanks for the reply andre,
using a bridge, i could get the dc full rectified wave, but I will be developing it further for power factor measurement once this part is done through, by detecting the zero crossing of the voltage and current, so i will have to go with half wave rectification to keep it simple. in that case, again, the microcontroller ground would have to be referred to neutral. Also i want the current consumption to be kept to the minimum.
Would it be possible to use the LM324 itself to interface both line and neutral to the PIC? The answer is somewhere in differential or instrumentation amplifier, but I haven't been able to figure it out.