You have to remove the struts to remove the springs. So you might as well do both at once, or you're going to have to pay $300 to install the springs and another $300 to install the struts a couple months later when they blow out.
Suspension work is not easy.
It will take a mechanic a good 4 hours to do, and the average person almost an entire day to do it.
EDIT: It would probably be more correct to say it will take a couple mechanics to do it. Suspension work is not a 1 person job unless you're particularly masochistic.
I've done springs in less than 2 hours, by myself? What mechanic do you have ?