We are on our first ever diesel and the DEF is pretty much a nonfactor. We add it as needed and just continue on.
As mentioned above, it's readily available nearly anywhere. Even places like Home Depot carry it.
We did just have a problem with the DEF indication in our 2016 GMC 2500HD Sierra. The "so many miles" to empty came on and it goes to a percentage remaining indication. That's always been the case and when I'll add more DEF. It usually comes on around 25% to go to empty. Anyway, this time it got to 24% left and I got some added, 2.5 gallons, and the 24% would not clear. Even after a week of driving. Took it to our GMC dealer and the tech was able to reset it with the scanner tool they use to scan for errors. Anyway, as far as using DEF, no biggie.