There is next to nothing you can grease in that system. A couple fittings at teh rudder box, but once its stiff, its normally too late.
You are going to need a new steering cable. If you are mechanically inclined, order one from Skidim and follow instructions around the internet to install. If not, drop it off at a shop, and have them put a new cable in it.
These cables wear out over time. I'd say if you get 500hrs or 4 or 5 seasons out of a cable, you have done pretty good.