Springs will give you a set ride height, where as coilover sleeves allow you to adjust the height. Full body coilovers such as D2, Function and Form, etc...can also allow you to adjust the stiffness of the shocks. To install springs, you must take apart the struts. Full body coilovers bolt right up, all you have to do is remove the OEM suspension. Alignment should be done after lowering your car, but wait some time for the springs to settle if they are new. Do a quick search on google for a detailed description, its not very difficult.