Should I replace the Leaf Springs?

Different springs have different arches to them depending on their application. It would not be unreasonable for one side to have a few more leafs in them because of the weight. I have seen leaf springs on HD vehicles under extreme stress every day and not lose their arch. A truck spring shop is your best bet. IF the springs check out ok a set of Goodyear air bags ( by far the best in the industry) would help to level out your rig as you adjust each bag independent of each other.