1. Mercruiser. No
2. Fel pro/Victor Reinz
3. If yours has rails, clean and reuse
4. Up to you. Interlux Bilgekote
5. 1/4-20 bolts, 5/16-18 studs/nuts in the corners. Again, up to you but if me I'd clean and reuse if not damaged
As others have said, pull the motor completely and mount on stand...