I wouldn't recommend connecting the probe directly to a microprocessor.
You need to use opamps with VERY high input resistances, eg TL071, TL081 (typically 10^12 ohms input resistance). Your run-of-the-mill 741 just won't make the grade.
You'll need at least 3 opamps - Buffer each side of the probe with a voltage follower, then put the third one in differential mode, using the output of the followers. While you're about it, give your differential amp a gain of about 10, maybe more, maybe less, depending on the input requirements of your ADC. THEN take the output to your microprocessor.