graft onto possibly dying Calamondin orange tree

I have a calamondin orange tree. The top part of the branches look dead and wilted and the leaves are wilted. I can see the green half way up the rootstock. I am wondering if I should graft on the rootstock of the tree where it is stilll green and alive. I am wondering if this will put more stress on the tree and totally prevent the top part of the tree from coming back. However I want to graft something on there while the tree is halfway alive to ensure something grows on it. Should I graft on this tree or wait to see if the top part comes back? I think it is going to be better to cut the top part of the tree off and graft something below where the top part used to be.