Speed sensor

I have a 1998 Jeep Wrangler TJ 4 cylinder 2.5 manual transmission, approximately 75,000 miles.
I think my speed sensor is broken because my speedometer and odometer do not work. I took it to Autozone because my check engine light came on and he hooked it to a diagnostic machine and it stated that it was the speed sensor. I asked where it was and he said by the rear drivers side wheel. I would like to know if this is true and how I can locate it and change it out.?