The hardest part about relining your chimney is fitting the chimney liner. You need to properly size the liner in order for the chimney to draft properly. Remember that there will be an extra inch or so around the liner due to the insulation. Chimney liner insulation is extremely important and actually helps to reduce creosote build up by keeping the chimney liner warmer. Chimney liner kits vary in price based on the diameter and length of the liner, but a basic, UL listed 6” diameter 20’ long chimney liner kit, complete with connector pipe, tee end cap, and top kit is $394.50. Chimney liner insulation kits, complete with all of the supplies needed to properly wrap your chimney liner pipe in insulation, runs $199.99.
As you can see you are saving yourself major expenses incurred from installation fees, but with that you are taking in some risk as well. Lining your own chimney can be very dangerous. You need to be absolutely sure you have enough manpower to handle this large, sometimes heavy liner or else accidents can happen.