Is it obligatory for the questioner to speak with her paternal uncle who has cut ties with her family and did not attend her mother's funeral, and is it incumbent upon her to contact him before her travel to perform the Hajj pilgrimage?

It is not obligatory to contact the uncle before traveling, but it is not permissible to sever ties with him. This is because a man's paternal uncle is like his father, and severing ties of kinship is a major sin. It is advisable to strive for reconciliation, as this is one of the greatest acts of nearness to Allah, and you may need him later.