lights on dash.

I just recently changed out the right front half drive axle because the
dust cover came off and everything fell out. when i replaced the axle i noticed that the ABS sensor was now covered with grease and dirt.
i cleaned the sensor off best i could and when i test drove the car i noticed that my "ABS, Service, and Trac Off" lights keep coming on.
I went and bought a new senor and replaced it last night at work.
I replaced the sensor and backed up about 15 feet and then started to go
forward and the lights came on again. I unhooked the battery for a good
30 minutes and tried it again and got the same thing. so i took the wheel off again and checked the wiring to see if it got damaged when the old
bearings flew out. i couldnt see anything initially. i just replaced both brakes about 5 months ago. the car is not acting funny at all.

so my question is, do you guys think it is more than a sensor, or do the
codes just need to be reset by a computer?

I'm going to take a guess here, but I suspect the sensor you changed was on the driver's side. J bodies have a very poor wiring harness to the front wheel sensors, the left side in particular. My '02 has had the l;ights on for over a year, just don't have time yet to try to fix it.
Disconnect the harness from the sensor, turn the key on ( don't start engine) and measure voltage across the pins, should read arounf 3.5 to 5V dc..I suspect yours will read zip, indicating the harness has broken inside the insulation. You can try to cut and splice a new section in, or get a replacement harness from Ebay or dealer/parts store, and splice in.
Jeff

actaully it was the passenger side sensor...same side as the drive shaft i replaced. but ill try that on both sides and see what i get.

Jeff has it right with regard to the wire harness. I had the same problem with my 04 cav. ABS, TRAC OFF, and SERVICE light would all come on, usually after backing up, and would only go off after turning the car off and back on again.

The culprit was the ABS wire harness on the LEFT FRONT wheel. I replaced it with Dorman P/N 970-007 (from AutoZone, for $38)

You have to splice in one end into the existing wires near the front bumper, but not a difficult job for the average home mechanic. Be sure to route the new wireharness with proper slack so it doesn't get 'stretched' when turning the wheels sharply.

Good luck,