As far spare parts for your, you would have find a parts motor. You can place a want Ad here on the AOMCI Webvertise section. There many members that have Champion parts motors. As for as the carburetor, retiredoz made an excellent suggestion for a carburetor kit or you can make the gaskets yourself.
Discount marine says they have the carb kit (Tillotson ME-1)
In regards to the ignition, test your ignition to see if the coil, points, and condenser are still good. If you need to replace the spark plug wires, then you should get 7mm copper core wires
and not the automotive stuff. You can purchase 7mm copper core wires at local lawn mower shop, Tractor shops, and some automotive shops. You can even get them on Amazon.com.https://www.amazon.com/Black-Spark-Plug ... +and+boots
If your coil is bad, then you will have to identify the type of coil and report back to the forum for suggested replacements.
Your gearcase uses grease and not gear oil. Good gear case grease are Corn Head grease and Lubriplate 105.