I'm driving a 96 honda civic and my car has been shaking and overheating?

I have check for leaks and everything is fine but i do have a rusted spark plug, i'm wondering if that may be the cause of shaking and excessive overheating to the point i'm driving with the heater on all the time. Can anyone let me know if the spark plug is the problem and if i replace this one rusted plug will the car drive back normally?

Excessive overheating? Does that mean you are losing coolant. A bad head or intake gasket could cause that.

Which end of the plug is rusty, the outside or the business end which goes in the engine?

If the outside you have a water leak dripping onto the spark plug: Fix the leak.

If on the inside you have major engine problems.

I doubt very much if you can buy just one plug, give your car a treat and buy a full set, they'll pay for themselves in just a few thousand miles