2005 Mazda Tribute ABS Light/Air Bags- --HELP!

My ABS light was coming on occasionally in my '05 Mazda Tribute and I was getting a thumping on my brake pedal. Brought it to dealer the dealer stated “the car had a bad right front axle ABS sensor ring.” According to dealer mechanic, 'axle would not come out and it was necessary to replace right front axle. I picked up the car and drove away and started hearing a chiming sound like a warning sound going on & off. Nothing flashed on my dashboard. I immediately returned to the dealer, they took it for a ride and heard it too. They had it for two days and then called and said they traced the problem to air bag light in dash. They stated they “removed clusted to check, found bulb can not be changed and would need dash cluster Reinstalled cluster and light now working but flashing a code They"checked system and found needs air bag module replaced. May also have cluster problem.” They are telling me that the right front airbag has to be replaced. Question: I didn’t have an air bag problem when I went in for ABS sensor problem. Now they want $600 for repair and they said that they did not cause problem. That they were working on the Axle and the axle is no where near the air bags.

I don’t know anything about cars…If they were replacing the right front axle, could they have done something to the airbags? How could I have gone in for ABS sensor problems and come out with now having to replace a front airbag?