The check engine light has been coming on when I stop for 10/15 seconds and the car is in gear (if I drop it into neutral this doesn't happen). I checked the trouble codes, as suggested by Ernie G. in some previous posts, and got 13 & 15 - Oxygen Sensor - where is this baby and how difficult is it to replace/repair it?

o2 sensors are located in the exaust lead pipes or manifolds, or both depending on how many you have. some have one, newer stuff uses four. yours are probably in the pipe(s). one two wire conector and screws into the pipe. i recommend if you can let the car sit a day or two, use a good penetrating oil, coke, or trans fluid to loosen the rust and debris from the sensor before you try to remove it. be carefull because sometimes you can damage the threads in the pipe and thats no fun to fix. if there is more than one o2 sensor, see if you can determine which one. if you cant, replace both.

The one wire oxygen sensor is located in the driver side exhaust manifold. Chances are, it isn't the oxygen sensor that's your problem. You may needlessly replace it and then read the same trouble codes. The code 13 indicates you have a problem in the oxygen sensor circuit. This could be a too lean or too rich condition, (or a bad sensor). You'll need to hook up a scanner to tell for sure. The code 15 indicates an open coolant sensor circuit. Unless you quickly discover that the coolant sensor is unplugged, a scanner will be needed to look at the signal the coolant sensor is sending the ECM.