dude, when you change the springs the shock comes right out so its just a matter of slipping the shock out and placing the new one on. So that would be what, maybe 5 minutes more for @ 4 corners.
Springs and shocks: 1.5-2 hours, maybe 3 if its a newbie
by the the way, that 2/3 sh^t threw me off, 2/3= two-thrids
