Someone once posted that they'd give up computers if they'd lose a hand. I wouldn't do that. - I can type with the stump, with a special stump sock, with the hook - and even with my prosthetic hand (Otto Bock system hand, voluntary opening), typing is no issue.

Key to happy typing using a prosthetic hand are two things:

• use a pen, bar, pencil, rod or any other cylindrically shaped long item to hold with the hand to activate the keyboard; using the hand itself you can type but not nearly as comfortably;
• use a good keyboard; I suggest a more heavyweight class A model (Cherry, Unicomp, IBM Model M or Das Keyboard), optimally containing both mildly concave key surfaces and relatively sturdy key switch mechanisms; other modern foil-switch keys may bounce when typing with the prosthesis, or the keys may not turn slightly oblique presses into clear up and down movements which well built key mechanisms are supposed to do (so I would not recommend these brands from my experience: current Apple keyboards, Futjitsu Siemens keyboards, some Logitech keyboards);
• if nothing else, give a keyboard a good try before buying it.