Overheated - Riser gasket question

[TL7]

Had an overheat issue yesterday, and after checking the impeller (was fine, changed it anyway), all fluids, etc I started the fake a lake and noticed dripping on the starboard side where the two nylon(?) exhaust manifold coolant elbows are. The front one is considerably more than the rear one. I will replace those, my question is should I go ahead and replace the manifold gaskets as well?

How big of a job is this for a regular joe, and any guidance or tips? Does anyone know the part numbers/equivalent of the gaskets for the exhaust risers?

As to the cause...if anyone has any theories let me have them, but the boat is 10 years old and we run almost exclusively in brackish water. We flush everytime, but in my experience I've seen that Father Time and salt always win, so may just be time to replace some parts.