Yeah, I think there are a huge number of faulty assumptions floating around about what it means to undergo "sex reassignment" surgery.

You don't make a penis out of a vagina. Doctors take a flap of skin, typically from the forearm or the thigh, and fashion a "penis" out of that. The complication rate is quite high (I'm linking you to a study but I warn you that there are some pretty graphic, unpleasant pictures attached to it. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901910/). Erections are replicated with implanted pumps.

Vaginas are constructed by inverting the penis. But again, there is the risk of complications (https://pubmed.ncbi.nlm.nih.gov/26218383/), especially if the person has been on puberty blockers, as the size of the penis correlates to the depth of the "vagina". As puberty blockers stunt penis growth, it's sometimes necessary to take skin from other places, such as the colon (https://www.mtfsurgery.net/mtf-vaginoplasty.htm) to achieve a functional depth. Patients then need to consistently insert something called a dilator to prevent the wound from healing over which, at least to begin with, is extremely painful. The vagina doesn't self-lubricate, but of course, you can just use lube.

Surgical techniques aren't at a point where you can change a penis into a vagina or vice-versa. As I said, I think a lot of people, including trans people sadly, are sold the idea the they'll have a normal sex life or be indistinguishable from the sex they want to be, and it's simply not true. I have no doubt that one day it will be. But I think we're a good few decades away if not longer.