1)
What else did Mano'ach need to know?
1.
Malbim: The angel said only what she should do, but not what the child should do (and she had not told about not cutting his hair). He wanted to know how the child must conduct, especially since it is a new Nezirus. A Nazir Shimshon is unlike other Nezirim, who may not become Tamei, and he may never cut his hair, unlike a Nazir Olam, who lightens his hair when it gets too long (Nazir 4a).
2)
What is the meaning of "la'Na'ar ha'Yulad"?
1.
Rashi: It is the child who will be born.
2.
Radak: It is when he will be born. Yulad is an adjective, like veha'Sneh Einenu Uchal" (Shemos 3:2).
