How does one switch custody of a child, and does the child's opinion have any bearing on the custody?

Assuming there exists a current parenting plan designating the mother as the primary custodial parent, you would need to file a Petition to modify the parenting plan requesting to be designated as the primary custodial parent. You would need to show that there has been a substantial change of circumstances that has arisen since the last parenting plan was entered and that a change of custody would be in the best interest of the child. It is a lengthy procedure which results in a full trial 11 months after the petition is filed. If you are contemplating fling such an action, please retain counsel because it can become very complex.

If there is not parenting plan, you would need to file a Petition to establish a residential schedule if you are not married to the mother. You would need to show that it is in the children's best interests to live with you instead of the mother. Again, please retain counsel before doing this given the fact scenario you stated in your question.