Well, the first thing you need to do is find out if it is the upstream or downstream sensor. Depending which one it is will determine how hard it is to change. One end of the sensor is a electrical connector that snaps in and out. The other end is almost like a spark plug. Use the proper size wrench or you can find a special socket specifically made for the O2 sensor and loosen it, pull it out, put new one in, and tighten. The two biggest problems you will encounter are location of the sensor and/or the sensor may be rusted to the exhaust. .
Any O2 problem should give a trouble code which is easy to pull on your Dakota. My 2000 Dakota only requires me to turn the ignition in a: on-off-on-off-on sequence. Your codes will show up inside the digital trip odometer on the dash. Once you know what code you have, you will know which sensor needs replacing. Expect to need a torch to heat up the sensor, so make sure you are replacing a bad sensor. If you look online, you can buy O2 sensors for about 40-50 dollars. Any other questions, give me a hollar. Gregg
Caution: use safety precautions and common sense when working on electrical components and under vehicles. This is my experience.
On my Dakota I used a 7/8 wrench, a straight slot screw driver for disconnecting the electrical terminals. Caution: The screw driver is only if you're having difficulty disconnecting the terminals. There is a small plastic clip holding the two connections together. If you use a computer to decipher the code be sure to write down the bank# and sensor# it may help to find the right sensor. On the 4.7 engine the left front sensor is the more difficult to access in my opinion. For this one, disconnect the terminal from beneath the vehicle 1st. Then break the sensor loose with the wrench by accessing it from under the hood. You get better leverage in case the sensor is really stuck in there.
Note: If possible to take the sensor to the parts store...DO. Apparently there was a change in manufacturing near the end of the year for my vehicle and I now have to use the universal sensors for the forward ones, unless I want to wait 3 days according to my parts guy. Hope this helped a little.
Another NOTE regarding replacement O2 sensors on the '00 4.7l - I had to replace my Pre-Cat O2 sensor recently and the replacement sensor's connector fitting didn't match the connector from the wiring harness. Turns out, that the Pre-Cat O2 Sensor from the '99 5.9l fits just fine (same connector). So you don't have to use the Universal sensor.