noticed a black wire that is not connected to anything. Does anybody
know where this wire should be connected? Also, I want to clean the

Probably a kill wire which goes to the magneto.
You usually pull this wire to check the magneto. If it starts, it's in the
wiing, if not the mag is shot.

carb and I wonder how to get replacement gaskets for the carb where it
attaches to the motor???

http://wss.lookupparts.com/Scripts/EmpartISAPI.dll?MF

Select the manufacturer in the specific catalog, then the specific engine
and then the gasket. Probably should rebuild the carb as well.