abs light question

hey guys i got a few quick questions hoping someone can enlighten me. i got a 2000 grand prix gt with 80,000 miles on it. about a month ago the abs light came on and i could feel vibration when driving high speed so i thought i would kill 2 birds with one stone and replace my front wheel hub/bearing assembly. well i bought the best front bearing i could find and installed them... started the car and the abs light was off, and it stayed off for a couple of hours... basically i am wondering if you guys think its a simple wheel speed sensor? maybe in the rear tires? but more importantly... to replace the rear wheel speed sensors, do i have to replace bearing and all as one unit like the front or can i replace just the sensor? answers to these questions would save me alot of time and effort even though i love to work on my car, just dont have the time right now. Also the traction control is off. or the light indicating that the trac control is off is on lol.

sorry for the long post just wanted to be descriptive and thanks alot for viewing it. hope to hear from ya! :p

Is it just te ABS light or are you getting a traction control system light (TRAC OFF) in conjunction with it? If it is just the ABS light then you may have other issues with the ABS braking system or it may not be anything related to a wheel sensor. Only way to tell for sure is to get it scanned with an ABS capable scan tool and see what chassis/abs DTCs are stored.

On all four wheel sensors you cannot replace just the respective wheel sensor but the whole hub assembly must be replaced.