It's not hard at all. Just a bit time consuming and if you're not carefull, painful.
You can do it at home with some jackstands but if you have access to a lift the job is considerably easier. Basically, you'll need to lift the car and remove the wheels. Up front it will be easier if you remove the rotor and move the caliper out of the way. I recommend spring compressors so you don't have to worry about the spring accidentally releasing out of the car. The strut doesn't need to come all the way out, just disco'd at the top and let the arm drop as far as possible. If you have compressors, the spring can be lifted out easily. without the compressors, you might need a prybar get the spring out. The rear is easier. Just disco the shocks and quads and lower the axle slowly to let the springs extend fully. Then just take them out. Since the lowering springs are shorter, they just go right in and put everything back together in the reverse order. You'll need to get an alignment and install offset rack bushings or Steedas bumpsteer kit for lowered Stangs. It's not that bad, just don't rush through it.
Eric