It is easy to renew a Philipino helper in HK. My helper also renewed by herself. I paid the gov't fee (~HK$400-500) and she did the renewal on her rest day (consulate also open on Sunday).
Long service payment: no need to pay her now. You got to pay your helper this kind of payment if you decide not to renew her and she has been with you for more than 5 years. However, if she leaves you some day after 5 years with you, you don't need to pay her long service payment!!
Cheap airticket: I saw from BK some days ago - Cebu airline. A BK mama said it is only $2xx + $1xx (tax)