The 2 bolts are your engine block drain plugs, the one with the large black piece is for the knock sensor. Trying to remember your engine/year, I think it goes on the port side, there should be a wire and plug that connects to the black piece. The other plug goes on the opposite side of the block.
The clamp is most likely off of the J hose, should be on the Starboard side, rear of the engine.
Yes, be sure to re-connect the garden hose, these are the exhaust drains. If not, you can sink the boat pretty darn quick. You should also replace the raw water impeller if it was not done last fall.