[travelin texans]

Dodge/Ram was the last holdout on the DEF.
In fact they had a commercial with Sam Elliot saying "while Ford & GM are stopped filling with DEF Ram is still out there getting the job done", but the contractor working for us had several new 3500 Dodges all using DEF & that commercial played every night for at least 6 weeks after they had those new trucks.
By buying the older truck you've missed out on probably 100hp & at least a 100 lbs of torque over the newer models, which increases every year in the hp/torque war between the big 3 trucks.
The DEF in my opinion is not a big deal, 2.5 gallons about every 3000-3500 miles equals about $12+/- if bought by the jug or $6-7+/- if bought at the pump at a truck stop. So far in 130k/6 years have only had 1DEF issue, had a recall on the DEF tank, they replaced tank & pump.