Its a pretty simple job. Drain the radiator, loosen bolts on water pump pulley, remove drive belt, remove pulley, remove the water pump bolts, might take a little tap with a hammer but the water pump will pop out. Give the o-ring on the new water pump a little shot of silicone spray before installing it then reverse the order for install.
There was just an article maybe 2 months ago in either Muscle Mustangs and Fast Fords, or Mustang Monthly abou how to change a water pump, pictures and detailed instructions, i'll look and see if i can find which one and which issue
Not hard at all but I had to knock the hell out of my pump before it would come off. I did take a large screwdriver and pry on it a bit to break it from the block. Otherwise it only took about an hour.