How would the body respond if a person took in excessive amounts of potassium?

Well potassium levels have to be tightly regulated in the body. You have potassium/sodium pumps in the cells in your body to make sure you have the correct amount of ions inside/outside the cell. For example. Your entire nervous system relies on a voltage potential that uses ion gated channel to propogate signals uses CL ions. These electricl ions are called electrolytes and are essential.

Hyperkalemia is the term for high potassium levels in the blood and one major cause is acute kidney failure. Potassium is needed for muscles to function correctly as well. Mildly elevated potassium levels are ok, but you have hyperkalemia your entire heart muscle and every other muscle can fail to function correctly