I saw a neat trick in I believe the latest Muscle Car Review. To remove the spring, you
partially close the hood to expand the spring, then insert small wood shims between the coils and when you open the hood, the spring will not be able to completely retract and you should be able to remove it.
I don't know of an easy way to put the spring back on unless you do not have to recondition it, in which case you would put it back on in reverse order. In the past, I have installed the hinge, raised the hinge to the open position (hood off), slipped on the front of the spring (hook toward front of car) and then used a large screw driver to leverage it onto the back hinge hook. I do this much the same as reinstalling a drum brake shoe spring. You might want to be careful with this one. I hope someone else has a better way to install the spring. Good Luck.