It's 180k miles. It's the 3.0L Duramax because the oil pump is on the backside of the engine using an oil submersed belt rather than a chain or set of gears. So you have to drop the transmission, exhaust, oil pan, and take the back side of the engine cover to replace a belt that should have been a chain. It _may_ be faster, to simply disconnect everything and pull the motor.

Source: I own one of these engines and I dread having to pay ~3k for this maintenance in 3 years. I like the engine, just not this maintenance ticket item.