I am having a problem with the ABS brakes on my S40 .

The ABS and Brake warning lights came on just after an axle change (something I am told is not related, but who knows etc) and both the dealer and local shop are not offering much that makes sense except that I should shovel additional thousands (well really $800) into their pockets.

Its not a full time thing, and the lights are not on after start up, and only come on after about 1/2 to 2 miles of driving. I have tested the brakes and the abs is deffinately not working after the light comes on, but does before it lights etc.

At first the dealer cliamed that it was due to the axle change and that the code they received was not detailing where the fault was, but later after questioning from the mechanic who did the axle repair they claim the code is for a faulty ABS ECM.

Issue is that I am not comfortable with this as they told me in person that these rarely go bad and can produce false positive type diagnosis on themselves (the abs ecm) and the fault may lay someware else. Since this is not a $100 repair I dont want to be paying the dealer to play parts swap backyard mechanic.

My questions are 1) does any of this seem to be right? 2) would it make sense to find an inexpensive replacment ABS ECM? ( I think I may have found one) 3) Are any special tools required beyond any programming etc 4) where is this located, and what does it look like?

Any help or ideas are appreciated, and I would really like to get this right because the rest of the car is in decent condition, and no matter if I keep or even more so if I was to sell it I wouldnt want to do that with any brake problems.

Thanks in advance