Don't listen to Polecat. polecats know more about applying odors than removing them. Seriously, vinegar, baking soda, vinegar and baking soda, hydrogen peroxide, and good ol listerene are the home remedies that are most useful, but they work best on fresh urine. Once its soaked in for a while, (what'd you say 120 years?) they don't work so well. It can soak way deep into wood and then the odor can spend a long time creeping back out. And its not just urine, tom cats spray a substance that smells almost as bad as...as...Polecat help me out here... No, wait, I got that backwards. Tom Cat spray is what folks use when describing other absolutly disgusting smells. They are almost as bad as tom cat spray. Tom uses it to mark his territory, and he tends to mark it repeatedly in the same place, it really soaks in and is harder to get rid of than urine smell.
There is no way to paint or seal over the smell, the odor molecules are smaller than the paint molecules and it comes right thru. You'll have to get an enzyme product made for the purpose, some pet shops have some, but better source of better product is janitorial supply. Use a lot of it and hope it really soaks in. Wait several days, they might have clothes pins at janitorial supply, if odor seems gone then seal prime and paint. And hope odor is gone. If enzymes don't work you gotta call in hired guns, they got some powerful enzymes and chemicals and machines, some really are "guns" that shoot stuff in and suck it out. Even then you are probably going to be ripping some wood out, which you should go ahead and do now with wall paper, "cardboard" backing (that used to be relativly common BTW), and any other absorbent or once absorbent material.
I too hope you ask many questions here, if for no other reason than to follow your progress in restoring a 19th century house, and the sometimes odd ways they did things back then ( they don't build um like this any more. Sometimes we should all be glad) I'm sure you will have many projects as exciting and fullfilling as this one, if not more so. Some day, it may be years down the road, but you will have a great sense of pride and an aching body from what you have achieved. People will say, with great admiration, "You certainly have a beautiful home here, now if you could just do something about that cat smell."
Measure twice, cut once.
Look at the nail, not the hammer. Watch the fence, not the blade.
If you hook your thumb over your belt you won't hit it with the hammer or leave it layin on the saw table.