Just replaced my pump at 42000 miles. Sounded like marbles in the pump.
Cummins Central Power can get the pump, but- they special order it from their supplier. They are BO otherwise, CCP said they have 75 on order but have no idea when they will ship.
Pump is $197 plus 15% overnight shipping fee. Factory is holding on to about 50-60 pumps for DOA use only.
Asked the service manager about changing it and he danced around the issue and quoted minimum 2 hours.
Got the pump and decided to try the home install route.
My son (17) and I had it changed in about 1:30 and we took our time. Follow the belt loosening instructions and 80% of the battle is over. 3 mounting bolts (#10 metric) and a hose clamp and you're back to the belt for re installation.
We did ours in a garage and it was 75 out, this wouldn't have been fun at night and snow blowing all over.
Cummins does sell a seal kit for the vacuum pump for about $10. Much cheaper than replacement if you can get by with it.