Sadie,
I have just read through this post and a lot of your other linked post, and honestly, I think you know what you have to do.
I have no new insights to add, the girls that spoke up before me hit everything that I was thinking. But, the one thing that my gut tells me, and maybe it is because I am projecting my own experiences on the situation, but since you are asking for feedback, here goes..
Yes, I agree, without your 'male part', your relationship with your GF will change into something even less committed, and may even end, and it may end even sooner than 1 year..
These are just my thoughts, I cannot KNOW the future, but I can see patterns, and extrapolate probabilities. Even as a 'trans' person, you having a 'male part' defines your relationship in your GF's mind, you have no control over that fact, and once it is gone, she will drift away. Just my opinion, based on instinct, experience, and probabilities.
From my own experience, even though I had broken up with my ex two years earlier, and even though she had a boyfriend, and even though I was already interested in men, there was still a 'something different' about me that kept her 'connected' to me in some way. Literally days after my surgery, that ended, and I was now no longer the creature that she had loved, I was now the woman that had killed her man. The death of my penis, marked the death of our connection. My ex also resisted my transition, but she also was willing to make accommodations, as long as I remained within the bounds of her comfort zone. Once I was without any maleness, I was dead to her.
Yes, I know, my thing with my ex was between us, and is not you and your GF. But, the parallels are there. It is about her, not you, and if you are to be true to YOU, it will cost you HER.
I hope I am wrong. But I also hope you proceed entirely based on YOUR needs, since her needs run counter to yours...
Just my two cents worth, and I know I am not saying anything that hasn't been said, nor anything you haven't likely already considered. But, hey, you asked, and i just got here, so there ya go!
I hope you have a great trip and an easy recovery, hun!
;-) Missy