Changing a light bulb can be quite an easy process, however, if you do not feel safe, consult an electrician. The electrician will take the necessary steps to change the bulbs. Below are some of the steps.
Generally, pendant fixtures should hang 6-ft from the ground to the bottom of the fixture. From the countertop, the bottom of your pendant light should hang between 30 to 36 inches above. This height allows for you to use the lit counter without having the pendant in the way.
Consult a licensed electrician for the installation and mounting of a wall sconce.