I actually have some experience with this. My husband had the fairly typical long, slow decline in kidney function. He was diagnosed with kidney failure in 2002, when it was discovered he had 30% function. He didn't need dialysis until 2008. By that time, he didn't really feel "sick" yet, but the doctors said it was time for dialysis, so of course he complied.
We were really anxious about dialysis since we had watched it slowly kill a friend, and it's true, it was no fun, but it actually treated my husband's body pretty well, and he never got any of the common infections. So, when, 18 months after he started dialysis, we were finally ready for the transplant to take place, he was more worried about the surgery and aftermath than anything else. Dialysis was the "devil he knew."
After the surgery, DH suddenly felt worse than he ever had in his life. We had a rejection scare after we had been home a week, so he went back into the hospital for 9 days. And his recovery, and getting used to the new meds, took about 4.5 months. So, for those 4.5 months post-transplant, he felt worse than he had at any time before, including dialysis.
I am not telling you to this to scare you, but merely to present a side of the story that's not often told. It seems that most transplant patients feel so much better post-surgery, that all of the hardships (the actual recovery, the new medications) feel instantly, totally worth it.
That was definitely not the case for my husband. But here's the bottom line: at that magical point of 4.5 months post-transplant, he suddenly realized that he felt better. Even good. And very soon after that, he began to feel better than he had in years. More energy, he could of course finally eat anything he wanted. No more edema. All the good stuff that comes with good health.
So, I don't really have any advice, just wanted to share my perspective. I, as the donor, wasn't nervous about anything. My husband was actually quite scared (both for me and for himself). And it turns out his worries were not groundless; he had a really rough go of it after the transplant. But, it did get better. A whole lot better. And truly, life is good for us now, health-wise.
Try not to lay any expectations on your brother about what he should or shouldn't feel (easier said than done, I know!). He's going through a lot and since he seems not to be the feelings/talkative type, it may be even harder in the short term, now before surgery, and for awhile after. But the numbers are in his favor for him to have a successful transplant and then to slowly (slowly) feel better and resume a "normal" life.
My sincere best wishes to you both!
Kara