Congrats, and you'll love it. I paid about a $6000 premium for the Cummins over the 6.4 when I bought my 2015, and a comparably equipped half ton was right in the same ballpark as the 6.4. Total no-brainer to go with the diesel as far as I'm concerned. I think you'll be happy with the current model Cummins too, with the old reliable CP3 fuel pump. If I were buying a new diesel today I would either find a 2018 Ram like you did or I'd jump over to a Duramax.
You won't regret the diesel. The only trouble mine has given me in the first 50,000 miles is a blown water pump, which unfortunately was replaced with another bad unit. It's now on the third and finally good water pump after a recall fix. It has had more recalls than I'd like but mostly they've been pretty simple and none have actually given me any trouble (aside from the aforementioned water pump).
