No, a custody evaluator and/or a Guardian ad Litem are not required.
A Guardian ad Litem is an attorney that is appointed to be the child’s attorney and speak on behalf of the child’s best interests. They speak to the child and advocate for what the child wants in terms of custody and speak to the Judge on their findings. A Guardian ad Litem is not necessary but is a good tool to use if you feel that your child’s voice is not being heard and you feel that the other parent is manipulating the child.
The judge can appoint these individuals on their own motion or you can petition the court to appoint one on behalf of your child.