you dont have to but it helps ride quality and will be lesws prone to blowing struts<<<<<

 

you dont necesarily need new shocks. Lowering the car will put more strain on your current shocks since they will constantly be compressed therefore your stock shocks wont last long. Aftermarket shocks are a good thing to replace at the same time that you do springs its just not imparitive to do it. Coilovers are a way to be able to adjust the height of the car. Its basically a spring with a threaded shaft that you can turn the perch on to raise or lower the car. Most importantly get an alignment done right after you lower the car. Your camber will be out so youll need a camber kit but more importantly get the toe corrected toe eats tires faster than camber.