Answer to Question 1
Drugs can alter the availability of the neurotransmitter in the synapse or affect the receptors by 1) mimicking the action of the neurotransmitter (agonist) or 2) occupying the receptor preventing the neurotransmitter from activating (antagonist).
Answer to Question 2
Steps involved are uptake of precursors; synthesis of the transmitter; storage in vesicles; release into the synapse; interaction with the receptor; reuptake into the releasing neuron; and metabolism by enzymes.