Same thing happened to us in 2012. Beaver Coach Service replaced the stripped one and the other one since they were a troublesome and defunct model. As I recall, Monaco had briefly switched to a cheaper brand ill-advisedly, and ultimately went back later; but our coaches were caught on the wrong side of the timeline. I think the good manufacturer was a Eugene area one.
Regardless, the labor and parts cost for us was $270, which included newer high-performance boomerang style blades at $46@. The 2 arms totaled $80. The service receipt doesn't layout the brand, but BCS part no. was 352-0125 for the arms and 23-6343 for the blades. You might ring up BCS parts for more information.
As Ed says, you need to know exactly which parts are damaged. If it's indeed more than just the arm, the cost will be higher than mine.
Joel