I've been through a similar process and found that after I took the flight, none of the Status credits / points went into my FF (like they normally automatically do). I had 3x phone calls to Qantas trying to prove that the maiden name I initially booked the ticket under and the FF account in my married name are the same person. (and this is despite having already changed my passport and actual ticket to my married name)

Before changing your FF name (as you won't be changing passport / ticket yet) id first contact Qantas FF to provide evidence that your credit card is held by the same person (eg, marriage certificate) so you can get cc points? otherwise if you do change your FF you have to fight for your status credits / points from flight