Does an electrician need to change the light fixture?
No, however, you do need an electrician to install a new circuit, This may be the case if you are installing a light in a different location. If you are changing the electrics in high-risk areas, such as a bathroom, it is strongly advisable to have an electrician complete the work.
If you are unsure if the wiring of your home is in good condition it may be advisable to get an EICR (Electrical Installation Condition Report) to check for any faults.