Thanks for all the great information and encouragement.
I am looking at replacing the entire exhaust system anyway. as well as the fuel lines and water seperator filter, maybe even the fuel tank if I can figure out how to remove the old one.
Most of the problems I anticipate involve the difficulty of removing old parts that have rusted up quite a bit. Especially the coupler. I am not sure about the bearing, since there seems to be some fixture on the outside of the hull that the shaft goes through that I assume contains the bearing.
I need to replace the propeller. Not sure yet about the shaft - it seems like it's in good shape, but I'm not sure how it will line up with whatever engine I go to.
I will probably have lots more questions as I get into this. Thanks for the help everyone.
I've had the boat for only a year, and I am most excited about the years to come having a reliable, adequate sized engine for a boat we really love.