Go to the Gen 1 suspension section there is a long thread on price, swap, etc.
As far as needing to do them right away, it is my understanding and I do NOT claim to be the sharpest crayon in the box, you may notice a ride diff on old shocks. Maybe not if this is your first Raptor and have never ridden in a new one, but you don't have to do or park the truck kinda thing. I have a friend who is just over 90k, on a street queen, has never had his shocks done and says he can tell no difference in when he bought the truck, so he plans to ride on till they leak. You are at the rite place here to get the shock thing explained