Hi, I am a lone female traveller and would welcome any advice no matter how small as I havent flown long haul before.

I fly from NCL to DBX on 6th Feb then on to AKL the following day.. I have booked the comp hotel room as there is a 10 hour transit wait in DBX. I have booked economy class as I couldnt afford business class, but I would like to know if its possible just to upgrade part of the journey.. I've flown to Dubai before and coped with the 7 hours, but the thought of 14 plus hours with my knees squashed against the seat in front is not appealing ( I am 5'10", with very long legs) There were no extra leg room seats left, but I have reserved aisle seats so that I can stick my legs out.
I'm assuming that I will be able to check my baggage in all the way through, but am not sure of the procedure through DBX. I have been looking at the meet and greet service in DBX and wondered if anyone has experience of this..
I have joined skywards and will be earning 25000 miles on this trip. Will I be able to use any of these miles on the return leg? (I travel back on 20th Feb).
Am I to understand that there are different classes of tickets even within economy, I keep reading things about Y J F and K.. its a bit confusing (and no i'm not blonde! )

Hopefully someone will take pity on me and offer some useful advice as I am starting to get quite apprehensive about it all.. feel free to message me if you woulld rather not reply on here.

Kind regards

PP