Hi, Trans Girl here currently serving in the AF. I dont know about the whole surgery thing honestly. I have not transitioned yet so I really have no experience with going through bootcamp after transition.
Understand that there are waivers for almost anything. Also understand that they are less likely to give out waivers for people joining than they are for service men and women already serving. I am not aware of enlisted careers that require a degree. From what I have seen, you get most of the education you need from technical school while you are going through the pipeline. In the Air Force, your technical training or "Tech School" will give you college credits which count towards your CCAF or community college of the air force degree. Which is basically an Associates degree. I dont know how other branches work so I cant really speak for them.
As far as I am aware the ASVAB is the same test no matter what age you take it at. It can kind of tell you what careers you would be suited for. It has sections that can show aptitude in certain areas. And certain career fields do require a certain ASVAB score. So if you want your options to be as open as possible, a higher score is better.
Bootcamp does actually kind of suck. I am not going to lie to you. There is nothing to be scared of though, its a pain the ass and there is a lot of stress and yelling and pointless BS. You will pretty much suck at everything in bootcamp and it will never be good enough. Honestly, as long as you give even a little bit of effort, keep your head down, and dont do anything stupid you will make it through bootcamp. Just remember, whenever you are getting yelled at, that its not personal, (unless you are on the shitlist), and that they are just trying to make you more resilient in a stressful environment. Thats really all bootcamp is, teaching people to follow orders, work as a team under stress, and to form a cohesive unit with people you have never met.
Anyway, I hope this answers some of your questions. Again I am in the Air Force, so some things will vary between branches.
Best of luck to you dude. :)