blown shocks will not cause you to fail emissions.
one way to tell if your shocks are blown is if you see oil all over the place on the shocks. another way to check is to push down on the rear and see if it bounces up and down. It shouldnt.
replacing the rear shocks is easy. one person can do it on his own. 2 people will make it even simpler. I think shops charge around 300-400 to replace all 4 shocks/struts. you and a friend can do all 4 shocks in 6 hours if its your first time. Less, if your friend has done this before.
if youre buying kyb's, you will reuse the stock mounts.