I would say NO, it's not difficult to take care of. I have had CFRD since 1996 and have participated in 3 marathons and play hockey three times a week. While working a regular 40hr job and providing for my wife & daughter.
It's a lot easier then being plugged into a wall for 2hrs on the vest and nebs twice a day.
However, you do have to stay on top of your blood sugars. If you flake and run high blood sugars, which I have done a few times, you can get run down and be more susceptible to CF illnesses.
But, if you stay on top of your CFRD it will not affect your CF. In fact, the insulin usually gives people with CF a bigger apatite which can lead to weight gain.....yaaaaahhhhhhh
Good luck & stay positive,