Most of it isn't too hard. You'll only damage your truck if you go crazy with the knife. I used this on mine.
You need to clean the beltline really well, then take your time, don't be afraid to unpeel and restick in some places. Make sure you have a heat gun because you'll need it for that back piece and the compound curve to get the vinyl to stretch just right and not get creases/bubbles. Make sure you tuck it around the top and bottom right. You'll also need the heat gun to stretch the vinyl around the ends like the part in the door creases. Watch some youtube videos and then go to it. The vinyl is pretty cheap so if you really mess it up just peel it off and start over. That kit I linked above has a lot extra at the end. Start with passenger doors, they are short without a lot of complications.
Also, that tape above has a clear protector on it that I didn't notice at first. I thought the finish scratched easy and looked like crap till I got a little part peeling off and then realized it had that protector. Looked much better once I peeled that off. Keep it on till you are almost done with a section.