ABS problem and fix

My 2000 K3500 deleloped ABS problems after they pulled the front hub for inspection for GMPP work. I took it back in and they had to replace the complete rotor, and hub assembly and sensor too to fix it as signal voltage was low from it. I think they damaged something when they tore into it the first time and if not for GMPP it would have been over 800 bucks which I think is steep (I have zero deductable) but if it had come down to them wanting me to pay for it we would have had words over it because it was fine until the tore into the hub a few weeks ago. A word to the wise.