DPF cleaning can cost from 400-700 bucks depending on where you go, if you willing to do some work and remove and install you can cut that cost down...Ive run DEF in several trucks and had no issues, my first truck was Freightliner with the Mercedes engine that thing ran like a kitten purrs, and got great fuel mileage, I did one DPF cleaning on 300,000 miles....you might need more if your east coast, stop and go, etc...
I dont think Id retrofit either, the miles add up and after you retrofit, youll wear something else out...I like the DD series and have had great luck with them...Ive always said I d rather have too much engine then less, if you need it you got it, but when your in the mountains and Loaded for bear, straining the guts outta a fuel economy motor is serious wear and tear, but there is a balance too...that DD13 has the guts and can be tuned to really pull./.