Air Filter Help

I have a 2003 F250 with the 6.0. It has a K & N filter and someone else installed it. I want to put the stock system back on the truck. I have a stock air intake system that I was able to purchase used. How hard will it be to swap this out, and remember that I didn't change this out in the beginning or could probably do it without asking for help. I just didn't see it before the K&N. Thanks, for all help.