Most of the gaskets will be OK. As mentioned, the impeller will be toast, replace before firing.
1.) MMO in the plug holes.
2.) Leave plugs out, lay on it's back with cover off and carb facing up. 1/2 cup MMO down the carb and pull the rope to suck it into the crankcase.
3.) Pull rope until you get oil splattering out the plug holes onto the ground/cardboard under the motor. Now you know there is enough oil in the motor to stand a fire-up.
You also know how it felt when you pulled it over. If it freed up and felt smooth'ish - you are on right path. If it felt gritty, you got issues ...
4.) Lower leg comes apart to change water pump impeller. Get book, or look at exploded diagrams on the web until you see exactly how to do this.
5.) Use Vaseline on all rubber mating surfaces when you re-install the water tube and any rubber bushings. Use it on the shaft splines going into the bottom of the crankshaft.
6.) Get a "nub" greaser. It's a small grease gun that does not really lock onto a zerk. It's a press fit onto grease nubs and it will feed a zerk unless it's frozen. Lube all points that have nubs or zerks.
Carb will prolly be OK, but needle and seat will be dry and powdery. Drop float bowl and clean them gently with nylon scouring pad until the needle is shiny. Make sure the float will move easily and will close off the fuel inlet.
Did you get a tank too? Fuel hose?
That's a nice motor - One of Mercs better ones