Right...
So you start the car and the ABS light should come on. Then after a few seconds it should go off. If there's a wheel sensor fault then the abs light comes back on acouple of seconds after you start moving because it's only then that it can see a discrepancy between what the 4 sensors are saying.
If the light just comes on and stays on (without moving) then it may not be the wheel sensor after all. The abs computer module does tend to take a dousing from clumsy coolant fill ups
The good news is you don't need to remove the whole module, you can take the cover off and replace the electronic part on top very easily. That's what I did on my old chamade with the electronics board from a calibra.