That lift kit will change how your truck handles and how it looks, but it is a heavy hit to the bank account all at once. Shops are usually slower in the winter, which is often the best time to ask for a deal on labor or parts if they have a slow week.
You are looking at about $1500 for a quality install. We can break that cost down so it doesn't leave your wallet empty, but you have to be disciplined about the math.
Remember that the 0% intro APR is just a window, not a free pass. If you have any balance remaining after the 15 months, the bank will start charging you interest on what is left, which will quickly cost you more than you saved.