Hi,

The first statement needs clarification:

If you mean people in Montenegro or Serbia, then you would use "Nobody in Montenegro or Serbia is prepared to invest in this new federation."

If you mean the countries Montenegro or Serbia (not the people), then you would use neither/nor: "Neither Montenegro nor Serbia is prepared to invest in this new federation."

You need to remove the collective noun (things) if you want to use the either/or, neither/nor combination.  In this case, you will rephrase them: "You won't be happy with either money or fame." or "You will be happy with neither money nor fame."  

If you want to use the collective, then you don't need the either/or or neither/nor combinations, as well as the individual nouns (money, fame): "You won't be happy with these things: money or fame."

I hope this makes sense.