The wires CAN be changed with the manifold on if you have small and/or flexible hands. But it is far from easy, and you had better know the routing like the back of your hand. You must remove the cowling, wipers, and fuel rails however. You can use a square wood "shaft" from a hobby store or the back end of a wooden brush to pop the coil ends on. Before taking the manifold off, try getting your hands into the manifold to pop them off. If you can pull them off, you should be able to put them on as well.
Not Joking: Keep a bottle of dish soap and a cell phone handy. If your hand gets stuck, you will certainly thank me later.