Carol,
"Tube feeding" is highly unlikely. Unless someone is just using the wrong words. He will have an IV. That keeps fluids going while he can't ingest any.
There is something called TPN. Because I had complications (ileus) I could not eat or drink anything for an extended period of time so they put me on that. There are three bags of different types of things that basically pump into his veins the resultant nutrition similar to what would happen if digestion had actually happened and enriched the body nutrients. Here is a link:
www.nlm.nih.gov/medlineplus/druginfo/meds/a601166.html
Again, that is only probable if he winds up having an extended stay. "Tube feeding" is when a tube is put up the nose (or through an incision in the abdomen) and then into the stomach. That's for people who can't swallow. Sometimes stroke patients need that.
It is HIGHLY unlikely that he would have to wear adult diapers for the rest of his life. If that were the case people would not bother getting neobladders. They'd get an Indiana Pouch or ileal conduit (external bag). Over 95% (I think its even higher but I can't find the number right now) of men regain day time continence. A little more than 90% of men regain night time continence with the neobladder. I was in the unlucky few that didn't get night time continence back. What I just do is wear a condom catheter when I sleep and it is hooked to a catheter bag. I don't wear pads or diapers. Some guys wear the pads because of very minor leakage during the day but usually that resolves with maybe the exception of coughing or laughing hard or something like that. Some guys even wear panty shield things because it's such a small amount of leakage. As for me, I don't do anything special during the day.
If your mom is healthy it is likely he would not need any home health care. For someone living alone it would be highly recommended. Most things he can do himself or with a little help from your mom.
As to sexual function, that can vary in the time it takes. Yes, they always take the prostate. The risk of spread is just too high. Nerve sparing is important to retain the feeling. There are also things his doctor will work with on for regaining erectile function. There will be no ejaculate (well...you asked) but there are still orgasms in every other sense of the word. It can take anywhere from a few weeks (although he wouldn't have the energy for it at that point anyway) to a couple of years for normal erectile function to return but there are things (pills or shots or other) that he can use in the interim. Lots of guys need that just due to age so it isn't really a big deal.
The lack of erections after the surgery is actually going to be a godsend for the other problem he is concerned about. The biggest problem for most guys with a catheter is that men have spontaneous erections. Erections cause that catheter tube to have some issues unless it is well lubricated and even then it never seems to be lubricated enough. I think they say there are typically at least four erections during sleep. That is one of the big causes of pain with the catheter. The other thing is there will some numbness just due to nerve shock and other things after the surgery so the catheter really is not such a problem.
He will likely have it for 2-3 weeks after getting out of the hospital. I thought this information was in the surgical recovery link I posted for you earlier. If you haven't read that, please go back and read it. It talks about all sorts of expectations and what to do.
Let us know if you have any more questions. Be sure to read those links and give him the information on the kegel exercises and such.
Tell him there are bunch of us here who have had the surgery he is facing. Some are just done with surgery and others of us are years out from our surgery. We are more than happy connect and he can ask us anything he wants.
Mike