"Cần" means " to need" and "phải" means "must" or "have to". "Cần phải" can be simply understood as "to need to do (something)" with more emphasis on the necessity of something needs to be done.
It is used in both formal and informal context. Actually, you can find it in many articles.
"Thanks a lot again" is "Một lần nữa, xin cảm ơn rất nhiều" in Vietnamese.
Btw, "orange" is "quả cam", not "quyển cam", Raph. :P