I'd put those flappers back, in fact I bet OMC parts would fit. I had to replace mine after my bad overheat in the summer before this past.
The starter you should be able to get it out if you have room. Hopefully that damn fiberglass they like to have all around the rear of the engine is not in your way. I'd have to take the old starter and b!tch slap the designer with it if that were the case, lol...
On my boat I remove half the the rear seat, the engine bulkheads and slide the battery back. Then I can get it out in about 20 min.
Two bolts go up thru the bottom of the housing into the block. They were either 5/8ths or 9/16ths. I had to replace the starter (second one) from that same incident because it was full of salt water. Good thing they don't cost much. It's heavy helps to have strong arms, and a long 1/2 drive ratchet. An easy way is to tie a strong line around it and have someone you trust hold the line up above the engine, so you can get the bolts started, without having to hold up the starter with one hand and start the bolts with the other. If you have no helper, then lay a 2x4 across the gunnels, and tie the starter up around it at the right height and maneuver it in place. Necessity is the mother of invention lol....
I doubt any damage happened to the flywheel. At most you might replace the bendix drive. It actually didn't sound that bad to me.
You could bench test it or take it to an auto electric shop and see what they say.
https://www.dropbox.com/s/97y7b927tdgll ... r.jpg?dl=0