How much you buy pretty much depends on the condition of the components that are already there. I had lowering springs on stock shocks for about 60,000 miles, and then bought my sport shocks and springs. The minimum should be shocks and springs. But before you install, check out the other components, especially the balljoints, upper and lower. You don't need different endlinks unless you go with an aftermarket swaybar.
My suggestion for shocks in your case would be Monroe Reflex shocks, and get the ST springs, they ride pretty smoothly compared to others.