If I was you and you need to rebuild, I would pull the engine out of the sled and find someone in your area who is reputable at rebuilding engines and have them do it. One of the main expenses of rebuilding a engine is pulling it (I think Yamaha charges 17 hours?) Typically, it's going to be $800-$1000 in labor if you provide the parts and pull it your self. So the only thing you would be saving is that $800 or so by building it yourself and have a possability of putting it together wrong and be back in the same place you are now. Plus a lot of time a good motor builder can see little stuff you can't that needs taken care of, and do the little things it takes to do it right putting it back together. JMHO.