There are two ways. You either buy a roll of darkroom paper and do it all by yourself under the red light, or you can scan a negative or a smaller print nicely and send it away online to get a digitally printed thing back in the mail.
The digital option is the cheapest way to do things if you're going to have only one print made. Maybe it's the safest way to do it as well, as you don't have to struggle with huge papers inside a cramped and limited space. You just send away a digital file, and get the result back in the mail a week or two later.
Then, because you are some kind of snapper and darkroom printer yourself, you will start examine the thing down to the smallest pixle, I think. At least I would do, probably.
I would do the same thing if I printed the thing myself as well, and I would also most likely use a lot of paper and still not be 100% satisfied with the result. That's the backdraw of doing it yourself, actually. You would use tremendous ammounts of paper and get nothing on the wall. Again that's just a qualified guess.
So you would examine the digital print closely, and hopefully find no flaws that was not intended. Worst thing that could happen would be that it looked nothing like the file you sent away from your computer, which might actually be the case as you got no control at all. Imagine sending a perfect B&W snap away for some huge print, and when you open the received packet all your delicate highlights were quite clearly pink-ish... or blue, or whatever?! How would that fit onto that nice white wall you have been saving for a project like this? Or on someone elses wall. Someone else than yourself, who actually payed money to buy a print of your negative and then got something totally different to what they thought they would get?
There's this medic on board my ship who wants this snap I snapped some time last winter. It was a test frame just to check if that cannon-barrel-like 500 mm lens I got for my Mamiya RZ still worked. Snapped on some cheap-ish film, but looks quite nice in some way. A minimalistic B&W kind of graphic appearance that might fit nicely on her wall for all I know.
I have been thinking about printing this frame myself as well, but have not been able to get there yet. Fact is I want the print a bit smaller than the medicine lady wants her to be, so I might go for the darkroom option for my own print. She will have to live with the digitally printed stuff, I think.
I will make sure they make the thing onto some good and beautiful paper though, as I don't want her to get something done on some kind of "poster" paper or anything. I have seen enough of that. They are cheap, but the looks are even cheaper. Nope, we want this to look good as we want any snap to look good no matter which wall it's going to face.
Checking the online printer companies it seems it will cost a fair ammount of pounds shilling and pence as well.
It's probably worth it though, as it's a masterpiece all the way as you can clearly see.
So, it seems like this is the one she will be going for then. In this format, or something close to it. I think I will suggest a bit more height to it all, but then it's not my wall... This is 6x2 panorama format. Maybe 6x3 would add a bit more to the whole thing by getting a bit more dark blacks in the bottom, and some more paper white at the top? Well, I think I have to think about this for a few days...