My ABS light keeps coming on, along with the Service and Trac Off Light. Before I take it to the dealership, I want to try to save a costly bill. What or where should I check first? Will a diagnostic scan tool find the problem? or at least point me in the right direction....

Well I actually have the same problem,on my car it is most likely a loose connection or bad wheel speed sensor on my left front, you could use a scan tool to tell you what code it is most likely a bad wheel speed sensor or abs module. if you hook up the scan tool and it tells you its a bad wheel speed sensor you can unplug the sensor and ohm it with a dmm and look up the spec to see if it is out of specs. only other was to test it is with a oscilliscope which is like $1200,so you would have to take it to a shop.